The Migration Ecology of Birds
Ian Newton
Academic Press
This is an amazing book in that it contains fantastic detail about all aspects of migration yet it is written in an easily accessible format and style.  I highly recommend it to anyone with a modicum of interest in migration, and I have found it very useful for getting abreast of the latest.  Not that it is without items that are at least debatable, but considering the breadth and depth, it is without parallel.