Is there a book or author that has had a profound influence on your approach to life or therapy?

Back when I was a teenager, my favorite high school teacher introduced Kurt Vonnegut to me through Slaughterhouse-Five and as cliche it may be to say, it changed my life. Since then, I have dug into every other piece of Vonnegut's work that I can find. I love how every time I re-read anything by him, I find something new, intriguing, concerning, inspiring, suffocating, and enlightening - no matter where I am in my life. I have "So it goes." tattooed on my wrist for many reasons.