Epistle to white Christians / Fred D. Wentzel. (OCLC #1039631)
When cataloging, we look for the title on its preferred source of information (RDA) or chief source (AACR2) which for books is the title page. A cover or spine title may not be the authoritative title in the first place, but may also lose letters when damaged. Though the spine title on this volume is technically different from the one on the title page, I chose not to add it in a 246 18.