Start with high-confidence ecumenism books, then narrow by subgenre or adjacent topics.
A Doubter's Guide to World Religions
John Dickson
Common Prayer
Shane Claiborne, Jonathan Wilson-Hartgrove
Comparative Religion for Dummies
William P. Lazarus, Mark Sullivan
Prayers Encircling the World
Westminster John Knox Press
Judaism
Tzvi Novick
One People, Two Worlds
Ammiel Hirsch, Yaakov Yosef Reinman
Islam
James A. Beverley
The Hope of Liberation in World Religions
Miguel A. De La Torre
Triune Relationality
Sherene Nicholas Khouri
