I'm not sure if this is intentional, but there are a couple codex entries missing from the bosses section. All duplicates (indomitable vicious, Ke'eeng Ra'at in the silver challenge, and super duper meat man). Aditionally, the page with Ra'at Sied is unfinished.
EIDT: Oh yeah! You should probably remove the class challenge section from the monster classes. It always catches me off guard and is a little distracting.
We made an expansion and it is awesome. Really, you should check it out, especially if you're looking for some extra challenge.
Download over at ddmod.weebly.com!