You can pre-order the book via the Japanese Square Enix store. It will cost 2,970 JPY, which is about $19.75. In total, there will be 752 pages. As well, It seems that you will only be able to purchase a physical copy. If you get it from the online store, you can get a free, exclusive Sephiroth bookmark.
As for the contents of Final Fantasy VII Rebirth Ultimania, it’ll introduce all of the characters, setting, skill trees, abilities, enemies, maps, and more. If you want a complete walkthrough, you can just use this book, as it will also give information on important scenes like when you can affect your friendship scores with other characters. There are also interviews and Q&A with the staff at the end of it.
