I remember the first book that made me publicly cry. It was Bridge to Terabithia, and I was in elementary school and riding in the backseat of my parents car during summer vacation.
Most recently, The Art of Fielding had the honor of sending tears down my cheek in a public setting. I finished it while sitting in the first row of the airplane, soaring somewhere over the Atlantic ocean. This is a good book. I'd read a couple reviews of it, and while it was highly praised, a sports novel did not sound like something I'd normally enjoy. How wrong I was. I got hooked.
Chad Harbach is not an overly descriptive writer and is more of a storyteller than a painter, but as I read I was able to very clearly picture the characters and the book play out in my mind. It was almost like watching a movie. With twists and turns in just the right places. The perfect book for the summer.
If crying over a book in public isn't really your thing, I still love to recommend Tina Fey's Bossypants. This one flips the switch and makes you laugh out loud in public. Case in point, the other day a girl got on the subway and pulled out the book. I watched her out of the corner of my eye, waiting for the laughter that I knew was coming. Sure enough, she began to laugh and covered her mouth with her hand. I just smiled... the same thing had happened to me while riding the train.
It's a good thing, those books, that make you forget where you are and just enjoy.