Ah, I actually talked to someone about this fairly recently because of those weird elephant-seahorse things mentioned a few pages back.
The artbook covers both EO and EO2, it's basically a collection of all artwork generated for the games. There's NPC and character artwork, monster artwork, background artwork, and some promotional/extra artwork (stuff I've seen elsewhere, like the protector-girl in a bikini and gunner-girl handing over a present) by the character artist.
The book itself is actually pretty small if you compare it to normal artbooks or even standard magazines. The only artbook I have is about 11 3/4 x 9 inches, whereas the EO artbook is approximately 10 x 7. It's cute-small I guess, but I'd prefer it were larger. That's why I haven't bought it.
[spoiler]COUGH MAYBE SLIGHTLY NOT SO LEGAL HENCE SPOILER COUGH?
If you wanted a few images of specific monsters or something, I'd suggest e-mailing or getting in contact with the Feather from Nyleveia. (The someone I talked to.) They could probably help you out.[/spoiler]
To be honest, if it's for drawing reference rather than for growing a personal collection, I think you could use the sprite rips that were just released - especially since Himukai's art style is fairly simple and the monster sprites/backgrounds details are clearly visible even at their NDS size. Just my opinion, though.
If you missed it, which I'm sure you didn't, but anyway:
http://etrian.nyleveia.com/2010/01/05/e ... llections/