One book at a time? Or more than one? If more, are they different types/genres? Or similar?
(We’re talking recreational reading, here—books for work or school don’t really count since they’re not optional.)

Most of the time I read one book at a time. I tend to become engrossed in the book's story that it's not really an option to start another one when I haven't finished. If the book is a different type, i.e. educational, I could probably read it simultaneously with a fictional novel.