Update: Review for the English edition
戦場のヴァルキュリア2 ガリア王立士官学校 WORLD ARTWORKS (Valkyria Chronicles 2 World Artworks) is presented in a similar fashion as the first art book, 戦場のヴァルキュリア (Valkyria Chronicles) Development Artworks. It's thinner at 304 pages which is still quite thick. The dust jacket has a very fiber-like texture and beneath it is a highly glossy cover.
The video game Valkyria Chronicles II is only for the PlayStation Portable, which unfortunately I don't have so I can't comment on the completeness of the content.
Half the book is on the characters and the other half covers art for the tanks, weapons, backgrounds, storyboards and other miscellaneous art. What's missing is the narrated guide to the story. The artistic style is similar to the first book.
The character art section has the character profiles, their roles in the game, the designs including uniform changes. There are notes and little details relating to the game - basically things like how they relate to other game characters. There's even more character sketches at the back of the book.
The Weapons and Machines section covers the tanks, armed weapons and the soldier armor and equipment. The tanks beautifully designed and painted, as usual. As for the weapons, they are cool but aren't too many and the designs are minor iterations to those from the first game.
The background art are paintings and sketches with commentary. The places covered include the towns, buildings and various rooms. The architecture and set designs are beautiful. They are printed a bit small though.
It's a wonderful book but if you already have the first art book, everything feels awfully familiar. If you can only get one book, you should get the first one. Valkyria Chronicles fans should of course get both.
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Here's the Amazon Japan buying guide for your reference.