I used this book in conjunction with a Psychologist and found it to be the truest and most practical book on dealing with depression. It is in no way airy fairy or spiritual (I have no problem with spirituality BTW) it is practical advise on how to deal with your own issues and behaviour using CBT techniques.
I strongly recommend you use this book with a counsellor or therapist. As one other reader commented it can be a little overwhelming because it is so jam-packed with advice. If you are using it alone take it very slowly, read only a few pages a night max and take it from there.