I love The Road Less Travelled by M. Scott Peck. It was easy to read, and the chapters were in perfect order. I took special note that had I read some of the later chapters first, I would not have had the same experience. Each chapter prepared me for the next, and the explanations were clear and precise. The tone was very gentle and not at all critical or specifically judgmental, just observant. It is my favorite book because it helped me in my decision to be myself freely. It wasn't the first book on this leg of my journey, but it got me over a significant hump.
The most significant book before that was Are You Really Too Sensitive? by Marcy Calhoun. It was the first book that I'd read that gave me permission to fully be myself. Other books tell you that, but this one knew who I was and still said it.