Species: A history of the idea, by John Wilkins, is now available. I've ordered my copy.
I've known John over the net for several eons as time counts on the net, including seeing him write about species and the idea. For this central concept of biology, there turn out to be many different definitions that get used in practice, and probably all of them have changed through time as we learned more. Here, you get it all from the very earliest thoughts to the present. Likely not a middle-school or jr. high level read. John's a good writer, but his audience here is mostly the highly educated and knowledgeable. Still, I'll be giving it a go myself. Those who seriously interested in biology should definitely get a copy.
1 hour ago