Like most bookshops it carries an eclectic range of books that the proprietor got her hands on to copy! The sign on the door just says 'books from all around the world'.

Any foreign-language titles visible?

It looks like she carries Taldane and Kelish, mostly, and then one shelf up high is labelled 'distant shores' and has some Tien and some other harder to identify languages.

He'll save his Comprehend Languages until he finds a bookshop that carries more foreign titles, then; it doesn't last as long when cast from scroll... no, that's the wrong way to think about it, that potentially gives the Conspiracy too much time to catch him if his thoughts slip up.

Message to proprietor:  Hi, I'm shopping by scry today!  Sorry for this weird request, but if you can immediately go over to one of your books and open it to a section with something inside critical of Cheliax, in any way at all however minor, I'll immediately buy that book.  Bonus points if it's in a language that isn't Taldane.

(Yes, this is also testing whether the proprietor is being mind-controlled in a way that doesn't permit the controller to access native knowledge about their own books.)

The person at the desk, who appears to be a boy of about fifteen, startles. "Is this some kind of scam," he says suspiciously. "I'll call the watch." I need to be directed to whichever of the books we placed contains criticism of Cheliax.

      "No scam. My patron's just - very secretive and somewhat eccentric," Fennelosa says, and sets two gold coins on the counter. "Please do whatever he asked."

The boy snatches up the two gold coins. Bites them. "Alright then," he says. "I don't speak any other languages so I'm not gonna get the bonus points." 

And he picks a book off the shelf and starts leafing through it. "There's got to be something in here, because this is from Andoran and they don't like Cheliax one bit. Just give me a minute, okay?"

Sure, he'll give a minute.

- establishes baseline -

- too slow -

- too fast -

- how much should a bookstore operator know his own books -

"Ha! From a speech by the Supreme Elect Andira Marusek. 'If Cheliax declared the slave trade over, it would end without a shot fired! But Cheliax has embraced as their national philosophy this: 'it's not our problem'. And secondarily this: we're already saving the world, stop complaining. As if it would cost the ships that already patrol these seas a single penny, to make it known they'd stop slavers! They will tell you they have no means to, but the truth is this: they don't care to!! - 's pretty critical, I'd say."

      "Seems kind of unfair to me, really," Fennelosa says. 

"Does it have to be a fair criticism? I don't know what you'll count."

Keltham doesn't really have time to consider whether it's fair or not, he'll consider that later.  Right now he needs to spring his next test before hypothetical mind controllers have too much time to consider it.

Message to Fennelosa:  Buy that one and start flipping through it, random pages for me to read.

Message to proprietor:  Okay, now something critical of Qadira, fast as possible, will buy if you find it, same principle.

Keltham knows Qadira exists mainly because of browsing the Absalom history, not because anybody from Cheliax made any statements about it that they'd want to back up; and Qadira is pretty near here, and people in this region should have political opinions about it.  If they planted books about Cheliax here, and the mind-controller only knows about those, this request will take longer.  Likewise if it's all an illusion and they have illusions ready of particular books.

"I'll buy it," says Fennelosa. None of the planted books cover Qadira. 

       "Five gold." That's fine; any book from Taldor on recent history is going to say some critical stuff about Qadira, they've been having border disputes. 

"He's overcharging you by a factor of two or three," Fennelosa Messages the scry irritably. "Probably because he's noticed you're rich and eccentric. Should I haggle."

Message:  Just pay this one and mention that you'll only be paying 150% of the fair price on the next one.  I do owe him something for incidental exposure to all the weirdness around me, and a bonus for not being able to ask him about that part explicitly for information-security reasons.

Fennelosa counts out five gold, takes the book, and starts leafing through it. Publication date five years ago. It's about Andoran politics, mostly following the political rise of Marusek and a series of near-conflicts Andoran got into because its neighbors consider it to be sponsoring piracy. 

The proprietor looks for a book about Taldane military history, that should have some Qadira and some criticism of Qadirans. 

Timing on how long it takes them to locate that book versus the book critical of Cheliax?

Maybe slightly longer to find the book on Qadira but not all that much so.

And the criticism there?

This particular author feels that the Qadirans are the enemy of civilization itself and must be defeated in a fierce and immediate offensive rather than be permitted to erode Avistan's defenses, bit by bit; only when the last of them have been slaughtered will Avistan be safe. It is just as critical of Taldor's nobles, who it argues have grown too weak and indolent to hold the border against the Qadiran savages, and are derelict in their duties to themselves, their lands, and all of Taldor; the Qadirans, it argues, are a just punishment for the sins of the Taldane nobles. 

...that is more the quality of argumentation that Keltham expected of Golarion Authors, such as one might find in the library of an archduke's villa.

Okay.  Suppose that this bookshop contains some planted books, some non-planted books, and is missing some obviously problematic books which were quickly removed, by a team that teleported in separately and rushed ahead to carry out that operation and mind-control the proprietor...

Does the store have an obvious fiction section?  Keltham has been reading book titles whenever not otherwise occupied.

The separations it uses are 'romances', 'mysteries', 'histories', and 'business'. It's kind of unclear what's in each but the first two seem to be mostly fiction.

All right.  Buy the Qadira-critical book.

Then go to the 'mysteries' section.  How many books total?

About three hundred.

Right then.  Let's spend ten minutes on this.

Message:  Count off every fifteenth book starting on the third one, putting your finger on each such book so that I can see the title each time.  Then, open to three random places in each such book, and show each such random place to the scry sensor for six seconds.  Then buy them all.  You can haggle that time.

Keltham was initially thinking of just buying books that discussed magic or gods or afterlives, then considered that his fortress doesn't have enough books anyways.

If their mystery genre is at all like dath ilan's, if there's even a trace of sanity there, key obscure rules of magic should feature in at least some of these novels; and you can't rewrite fiction as easily as nonfiction.  The pages will be spoilers, unfortunately, but they should serve as a check against the books being rewritten or substituted before he can read them.

Fennelosa starts doing this, with some (but not much) visible irritation.

       "Careful with the books," says the boy. 

"I'm buying them."

      "Looks like you're waving them in the air."

"Well, aren't you a born genius. After I do that, I'll buy them. At a gold apiece."

      "They go for four normally."

"You're a bad liar, kid. In-demand books go for two in Cheliax, and Absalom has more trade, so it should be cheaper."

       "You're from Cheliax?"

"Yes."

        "Well, then, buy them in Cheliax, if you think they're cheaper there."

Keltham's not paying much attention to this repartee, which won't be very informative in the Conspiracy worlds where it matters.  He's scanning the book glimpses instead.

I couldn't keep my eyes off him. Always holding tight by the leg of the table with my hands and feet, I saw the miserable creature finger his glass playfully, take it up, smile, throw his head back, and drink the brandy off. Instantly afterwards, the company were seized with unspeakable consternation, owing to his springing to his feet, turning round several times in an appalling spasmodic whooping-cough dance, and rushing out at the door; he then became visible through the window, violently plunging and expectorating, making the most hideous faces, and apparently out of his mind.

I held on tight, while Mrs Joe and Joe ran to him. I didn't know how I had done it, but I had no doubt I had murdered him somehow. In my dreadful situation, it was a relief when he was brought back, and, surveying the company all round as if they had disagreed with him, sank down into his chair with the one significant gasp, ‘Tar!’

I had filled up the bottle from the tar-water jug. I knew he would be worse by-and-by. I moved the table, like a Medium of the present day, by the vigour of my unseen hold upon it.

‘Tar!’ cried my sister, in amazement. ‘Why, how ever could Tar come there?’

But, Uncle Pumblechook, who was omnipotent in that kitchen, wouldn't hear the word, wouldn't hear of the subject, imperiously waved it all away with his hand, and asked for hot gin-and-water. My sister, who had begun to be alarmingly meditative, had to employ herself actively in getting the gin, the hot water, the sugar, and the lemon-peel, and mixing them. For the time being at least, I was saved. I still held on to the leg of the table, but clutched it now with the fervour of gratitude.

Monseigneur Bienvenu had formerly been, if the stories anent his youth, and even in regard to his manhood, were to be believed, a passionate, and, possibly, a violent man. His universal suavity was less an instinct of nature than the result of a grand conviction which had filtered into his heart through the medium of life, and had trickled there slowly, thought by thought; for, in a character, as in a rock, there may exist apertures made by drops of water. These hollows are uneffaceable; these formations are indestructible.

When he conversed with that infantile gayety which was one of his charms, and of which we have already spoken, people felt at their ease with him, and joy seemed to radiate from his whole person. His fresh and ruddy complexion, his very white teeth, all of which he had preserved, and which were displayed by his smile, gave him that open and easy air which cause the remark to be made of a man, “He’s a good fellow”; and of an old man, “He is a fine man.”

He said this with such evident surprise that I was perplexed what answer to make, and the more so because coupled with something feeble and wandering in his manner, there were in his face marks of deep and anxious thought which convinced me that he could not be, as I had been at first inclined to suppose, in a state of dotage or imbecility.

'I don't think you consider - ' I began.

'I don't consider!' cried the old man interrupting me, 'I don't consider her! Ah, how little you know of the truth! Little Nelly, little Nelly!'

It would be impossible for any man, I care not what his form of speech might be, to express more affection than the dealer in curiosities did, in these four words. I waited for him to speak again, but he rested his chin upon his hand and shaking his head twice or thrice fixed his eyes upon the fire.

While we were sitting thus in silence, the door of the closet opened, and the child returned, her light brown hair hanging loose about her neck, and her face flushed with the haste she had made to rejoin us. She busied herself immediately in preparing supper, and while she was thus engaged I remarked that the old man took an opportunity of observing me more closely than he had done yet. I was surprised to see that all this time everything was done by the child, and that there appeared to be no other persons but ourselves in the house. I took advantage of a moment when she was absent to venture a hint on this point, to which the old man replied that there were few grown persons as trustworthy or as careful as she.