Update (7/23/2018): Title was changed to Diablo Bestiary: Book of Adria. The front cover still doesn't look to be the final artwork, because the title doesn't display the "Book of Adria" portion yet. The overall color scheme does reflect that Diablo III: Reaper of Souls bestiary is covered in the book.
Diablo Bestiary: Book of Adria Pre-Orders Open
Diablo Bestiary: Book of Adria Pre-Orders…
Diablo Bestiary: Book of Adria Pre-Orders Open
Update (7/23/2018): Title was changed to Diablo Bestiary: Book of Adria. The front cover still doesn't look to be the final artwork, because the title doesn't display the "Book of Adria" portion yet. The overall color scheme does reflect that Diablo III: Reaper of Souls bestiary is covered in the book.