Burn After Reading

I found all of the items needed for the achievement in the room after the the boss "Mana Devourer". Once you return to normal size just click on sealed tomes until you get them all. They respawn after some time.

In a single run I found 27 tomes total: 3 tomes in Moroes' room on the dining tables, 6 on tables and shelves in the Upper Livery Stables (area above Attumen the Huntsman), 9 on tables and chairs in the first and third rooms of the Guest Chambers (heading toward the Maiden of Virtue), and 9 tomes in the Library after Mana Devourer (don't forget to check upstairs part as well). I was able to get all 4 needed for the the achieve from those I found in Lower part of Kara, but it is RNG, however most people should be able to get this in a single run, especially if you are running it solo.

Sastron is correct about the books. Be looking for red, blueish, and blackish books they stick out very easily. Took me a bit to get all 4 but rng is rng.