The Tavern

Since the removal of burn spellbooks, and the addition of the spell library, there's no reason to not pick up books under trog any longer, having the spells in your spell library doesn't impact Trog in the slightest, and on the off chance you want to switch gods, having the spells in your library already saves you tedium.

Since it's never optimal to leave books on the ground, even while worshipping Trog, they should be set to auto-pickup unilaterally.

Seconded. I just played a game where I went Trog->TSO for extended and got to play the "ctrl+f for every spellbook in the dungeon, fast travel to it to pick it up, waste some food and piety(*)" minigame. It was not fun.

(*) the reason I wasted piety was because I already did one level of crypt after switching to TSO before realizing I needed spells.