The Mormon Illusion: What the Bible Says About the Latter-Day Saints by Floyd McElveen is his introductory comparative religion guidebook, apparently
cum bonus polemic, which according to the reviews is some sort of unflattering (and none too accurate) evangelical take upon the tenets as well as the perceived relative Christianity of Mormons (I've heard that there are some weirdly stringent requirements for co-religionism among certain sects, which apparently Baptists do not consider Catholics eligible for, which is basically pretty much in keeping the rather schismatic nature of historical Christianity

), free for a limited time courtesy of Christian publisher Kregel.

I like how this is filed (and currently the #1 bestseller) under Religion & Spirituality > Occult > Cults & Demonism in the Kindle store.

(Also, it has no Kindle preview, and may be a lingering Topaz or Print Replica format.)
Currently free, probably just for one day @
Amazon (available to Canadians & in the UK). Price-drop-check linkage for
Google Play, where this may become or already be free outside Canada.
Description
This classic work on Mormonism, now with over 135,000 copies in print, has been revised and expanded by the author. Major Mormon practices and beliefs are explained with thoroughly documented references to original Mormon sources. Chapters include: Joseph Smith--Prophet of God? The One True Church Priesthood and Genealogies Mormon Salvation.