The Upward Spiral: Using Neuroscience to Reverse the Course of Depression, One Small Change at a Time. by Alex Korb PhD and Daniel J. Siegel MD.
I found this book to be a fascinating book about depression. Not only does it explain the scientific understanding of what happens in a depression but it also provides suggestions on how to interrupt the down spiral of depression and to begin spiralling upwwards out of depresssion. Highly Recommended