Start with high-confidence christian history books, then narrow by subgenre or adjacent topics.
The Historical Figure of Jesus
E. P. Sanders
Willing to Believe
R. C. Sproul
The Immortality Key
Brian C. Muraresku, Michael Pollan
Black Religion in the Madhouse
Judith Weisenfeld
Turning Points
Mark A. Noll, David Komline
Marcion and Luke-acts
Joseph B. Tyson
The Age of Reason
Thomas Paine
The Unknown Life of Jesus Christ
Nicolas Notovitch
Fox's Book of Martyrs
John Foxe
Martin Luther's Ninety-five Theses and Selected Sermons
Martin Luther
Large Catechism of Martin Luther
