There are two new official Five Nights at Freddy's books due for release later this year. Both are official with Scott Cawthon listed as the primary author, so they should be quality. There's the updated edition of the Freddy Files, which should hopefully contain notes on the latest games. Also, there is the graphic novel version of the very popular Silver Eyes, the authors are registered as: Scott Cawthon (Author), Kira Breed-Wrisley (Author), Claudia Schroder (Illustrator).
The Freddy Files: Updated Edition is due for release July 4, 2019. The Silver Eyes (Five Nights at Freddy's Graphic Novel #1) is due for release 26 Dec 2019.