It is a collection item, with 104 pages of illustrations and artworks from the talented Dominik Mayer, the artist behind Fantasy General II.
In the book, you will also find more details on the background lore of the world of Fantasy General II, on the playable factions and on their units as well. You can find more information on its product page.
Furthermore, the physical editions of Fantasy General II - Invasion (base game) and Fantasy General II - General Edition are now available.
Both editions also include a physical copy of the Art Compendium book, so if you still haven't acquired Fantasy General II and you would also like to get your hands on the book, this is your chance.