The Re-Emergence of Emergence is a collection of thoughtful essays on emergence. I read this initially last year (?) but keep coming back to my favorite essay of the book by Terrence Deacon, Emergence: The Hole at the Wheel's Hub. Deacon's thesis is: "emergent phenomena grow out of an amplification dynamic that can spontaneously develop in very large ensembles of interacting elements by virtue of the continuing circulation of interaction constraints and biases, which become expressed as system-wide characteristics. In other words, these emergent forms of causality are to a curious type of circular connectivity of causal dynamics, not a special form or causality." Deacon goes on to make a pretty compelling case.
As one other reviewer noted, there are parts of this books which are pretty technical (for the Deacon essay mentioned above, I liberally used the dictionary and a couple of science reference books in my library)---that said, this volume is worth the price.
Highly recommended.