A number of years ago, a friend in Istanbul mentioned several times that many of his friends and acquaintances in classical music, cinephile, and other high culture circles in the Turkish capital were crypto-Jews. I had no idea what he was talking about until I did some research into the Donme (or Donmeh or other variant spellings), and discovered that they were the descendants of followers of the Jewish False Messiah of the 1660s, Sabbatai Zevi (spellings vary), who after Zevi's apostasy, had publicly converted to Islam but had continued to worship Zevi, and remained a small, endogamous elite who played key roles in Turkish revolutions and subsequent life.
For example, the foreign minister in Turkey's most recent Kemalist party government, Ismail Cem, was a Donmeh. (Perhaps a certain amount of the former neocon ardor for Turkey as the Good Muslims, which was so rudely interrupted in early 2003 when the Turkish parliament voted to not allow the U.S. to use its big base in Turkey to invade Iraq, much to the surprise and dismay of Paul Wolfowitz, had to do with Americans and Israelis being used to dealing with Turkish diplomats with many of whom they felt culturally compatible.)
It's wild stuff in an Umberto Eco sort of way, so, back in 2006, I wrote four long blog posts about them. The Donmeh are representative of how in the realm of the old Byzantine Empire, things are lot more, well, byzantine than we poor dumb Americans assume. We think of Muslim lands as uniformly Islamic, but there are millions of people there who are only vaguely Muslim, like the tens of millions of Alevis in Turkey and the ruling Alawi minority in Syria, not to mention Gnostics and Lucifer-worshiping Yezidis in Iraq.
Kirsch's review confirms the history I reported, but when he gets to recent generations after Kemal's revolution, he more or less announces, "Nothing to see here, folks, just move along, nothing to see. This topic is much more boring than it sounds. It's purely of antiquarian interest."