Start with high-confidence cults & new religions books, then narrow by subgenre or adjacent topics.
Cultish
Amanda Montell
Cave Mountain
Benjamin Hale
Urban Apologetics
Eric Mason, Isaiah Young
Urban Apologetics: Cults and Cultural Ideologies
Eric Mason
The Sullivanians
Alexander Stille
Inside Scientology
Janet Reitman
When the World Didn't End
Guinevere Turner
The Orwellian World of Jehovah's Witnesses
Gary Botting, Heather Botting
Oneida
Ellen Wayland-Smith
Waco Rising
Kevin Cook
A Thousand Lives
Julia Scheeres
The Road to Jonestown
Jeff Guinn
Cults Like US
Jane Borden, Simon & Schuster Audio
Counting the Cost
Jill Duggar, Derick Dillard
The Cult of Trump
Steven Hassan