My third book, Sects, Lies, and the Caliphate: 10 Years of Observations on Islam is available on Amazon, both print and Kindle versions (as of 1.19.16). 

My second book, Ten Years' Captivation with the Mahdi's Camps: Essays on Muslim Eschatology, 2005-2015, is (as of 11.30.15) available on Amazon for Kindle and other e-readers, as well as in paperback version.

My first book, Holiest Wars: Islamic Mahdis, their Jihads, and Osama bin Laden (Praeger, 2005) is more scholarly (it's my doctoral dissertation-turned-book), and over-priced--but still worthwhile.