I went on a little reading binge on books about sleep. Understandably, they covered a lot of the same material (but not exactly the same) and each one had a distinctive style to it. For comparison here are the books I read (in order):
1) The Secret World of Sleep: The Surprising Science of the Mind at Rest by Penelope A. Lewis
2) Dreamland: Adventures in the Strange Science of Sleep by David K. Randall
3) Sleep: A Very Short Introduction by Steven W. Lockley
4) The Secret Life of Sleep by Kat Duff
I was looking mainly for scientific information, in conjunction, perhaps, with interesting anecdotes. Dreamland by David Randall was the closest to what I thought I was looking for and I highly recommend it for anyone interested in sleep. The Secret World of Sleep by Penelope Lewis and Sleep: A Very Short Introduction by Lockley were a little more purely scientific. However, among these two I strongly preferred the no-nonsense style of Sleep: A Very Short Introduction. By comparison, The Secret World of Sleep felt like an academic paper that had been hastily modified by a copy-editor to read like a popular science book. The result is not-very-exciting writing that is larded with "accessible" descriptions and analogies. The amygdala is referred to at least a dozen times by the epithet "almond shaped". The first time was fine, the fifth time was patronizing. But I powered through.
I cannot recommend Kat Duff's book, because of passages that give serious credence to the explanation that hypnogogic hallucinations are in fact visitations by evil spirits. See my review there for more details.
The best thing about Dreamland is that it responsibly covers the material while being written in an engaging and entertaining style. I suggest reading it along with (before or after) Sleep: A Very Short Introduction which is drier, but reads fast and provides a lot more detail about the science (if that's your thing).

