I belong to Goodreads and one of the things I really like about the site and its community is the endless array of lists that the readers have put together. Just out of curiosity, I went over there to see what they had to say about X and I found this list of books with titles beginning in X.turns out the list was created specifically for bloggers doing the A to Z challenge, which I appreciate. Ihad to go down to number 15 before I hit a book I'd read, Lynn Hamilton's The Xibalba Murders. the first in her series of mysteries about Lara McClintoch, an archaeologist. There were 11 books in the series, with the last one coming out in 2007, the year before her death.
As it turns out, the only other book I've read on the list (which includes titles from writers as disparate as Edith Wharton and Andre Norton) is #27, Walter Greatshell's Xombies.