The first time I heard of Three Men in a Boat it was while reading To Say Nothing of the Dog by Connie Willis. Part of her story pays homage to Three Men in a Boat, and both stories are enjoyable.
I laughed out loud several times at the antics of George, Harris, Jerome, and Montmorency. I loved the British humor, the slapstick, the sarcasm and tongue-and-cheek remarks. The book was an entertaining and (mostly) pleasant trip down the Thames, and I can't imagine spending it in better company than with these three men and their dog.
Several times I thought of Mark Twain's writing as I read this, in particular Life on the Mississippi and The Adventures of Huckleberry Finn. This book was significantly shorter than those two stories, and I wouldn't really say that it was laced with social commentary, but it was every bit as humorous and interesting as those works. Well worth it if you need a quick pick-me-up and a good laugh or two.
The version I listened to on audiobook was narrated by the marvelous Hugh Laurie, and I am certain that his narration enhanced the humor even further.