Over at HiLobrow, io9 contributor Joshua Glenn has been posting scans of books from his collection that include the letter X in their titles. Not surprisingly, many are scifi. Where are all the X titles of today, I wonder?

Glenn writes:

This summer, I've been scanning and posting the covers of my "File X" collection - i.e., paperback novels from the 1940s-70s the titles of which include a freestanding letter "X." There are several SF novels, of course, including Andre Norton's "X Factor," Theodore Sturgeon's "Venus Plus X," and A.E. Van Vogt's "Earth Factor X." Interesting to note that three or four of the SF novels in my collection were retitled at some point to get that "X" in there...

via HiLobrow

A collection of vintage XXX covers from science fiction

A collection of vintage XXX covers from science fiction

A collection of vintage XXX covers from science fiction

A collection of vintage XXX covers from science fiction

A collection of vintage XXX covers from science fiction

A collection of vintage XXX covers from science fiction