I've defeated Malestair, and am trying to eliminate all of the quests in Dragonspyre. One of which has me searching for the books.
I've found them all, except for the one in the Hatchery, which is supposed to be in the Tower of the Homunculus. I found the tower, but the cygil is not lit, and I cannot start the instance dungeon.
Make sure you've done all the side quests in that area, because Homunculus is hidden behind a side quest. If you think you did them all but aren't getting inside ... that means you missed one. There's a dragon NPC named Sunbrand hidden around a corner, if I remember right. Use your "Find Quest" option to locate him.
Sunbrand will at first ask you to defeat some terror wings, then defeat Avalanche, and then after that you will get the quest to defeat Homunculus and get to the books.
This is his first quest that will get you started:
Alia Misthaven