I had a hard time with "The Power of Now" but I loved his second book "A New Earth." I would say it was life changing for me, in understanding myself and others. I think it contains all of the same ideas as the first book but told in a different way with some new additions and what not. I may be due for a re-read soon - It's been a while.
RE: Book review: Eckhart Tolle - The Power of Now.