Start with high-confidence religious lives books, then narrow by subgenre or adjacent topics.
The Historical Figure of Jesus
E. P. Sanders
Inside Scientology
Janet Reitman
Seven Men and Seven Women
Eric Metaxas
He Leadeth Me
Walter J. Ciszek S.J., Daniel L. Flaherty S.J.
A Textbook of Hadith Studies
Mohammad Hashim Kamali
Dipa Ma
Amy Schmidt, Joseph Goldstein
Rich Mullins
James Bryan Smith, Brennan Manning
Autobiography of a Yogi
Paramahansa Yogananda
