It came out for the 1st anniversary IIRC, so it is a bit limited on the art compared to the game now. The art only goes up to the first batch of summer characters with some exceptions like GMars’s that got used later on. That being said though, the book itself is pretty big, really high quality, and it’s a little over 300 pages. It near all the art up the to cutoff point I mentioned, including all the characters in their 5* arts (including the unused ones like Zethia, and non-gala versions of Sarisse and Mym, as well as the FEH characters) , all the dragons, full raid boss art, wyrmprints, story art, a few of the minis comics, and some of the general promo art. Besides all that, I really enjoyed seeing all the concept art they included. It has a lot for the main cast, especially Euden, and some for the dragons with how they adapted some of the Knights of Glory designs for the game, plus a few different designs of Mars.
Here are a few pics of the art it has if you’re curious:
Overall, even if it might more or less be a display item that’ll sit on my shelf that I’ll only look through from time to time, I’m super happy with the book and I absolutely think it was worth getting!