Sakura Wars is a popular Japanese RPG dating sim game franchise owned by Sega, the first game was released in the 90's, with later on 4 sequels being released since then (1996-2005). In the west, the Sakura Wars franchise was basically non existent. Of the first 5 games, only the fifth entry (Sakura Wars: So Long, My Love) got a localization for the PS2/Wii.
Much later in 2019 a sixth entry titled Sakura Wars (New Sakura Wars in Japan) got released which is a soft reboot for the Sakura Wars series. The game also released in the west in 2020 for the PS4 and got an anime series which was seen as a sequel from the soft rebooted game.
With the soft reboot, they are using a new character designer: Tite Kubo (known for Bleach and Burn the Witch) whom did the character designs of the main characters and their weapons.
Sakura Wars Setting Material Collection is an art book based on the soft reboot Sakura Wars game. The art book contains ~250 pages with character designs from Tite Kubo, artworks, mecha and monster designs, game designs and ingame pictures.
A fun to look at art book for any Sakura Wars fan. If you have never heard of Sakura Wars before, check out the newest game on the PS4 or play the first Sakura Wars game on the Saturn which got a fan translation.