The best "life-changing" books to give as gifts

My friend Tiffany asked this question to the interwebs:

"What is the best book you ever received as a gift or bought for yourself? Not a beach read, but one of those page turners that changed and/or improved your life."

And the interwebs responded, and I thought I'd slurp them all up and deliver this comprehensive list of life-changing books to give as gifts. I'll go first…