Kitab al Khazari, in English translation

"Framed as a dialog between the king of the Khazars, a Central Asian kingdom, and a Rabbi, the Khazari is an exposition of late medieval Jewish philosophy. Legend has it that the king of the Khazars held a symposium to decide whether his people should convert to Judaism, Christianity or Islam. This book is a fictional account of the Jewish side of this debate. Judah Ha-Levi, the author, was born about 1080 C.E. in Muslim-controlled area of southern Spain."