If all you know of Roald Dahl is Charlie and the Chocolate Factory and maybe one of his others (Matilda, Witches, James and the Giant Peach, &c.), I must recommend that you visit some of his short stories. I've just finished the Everyman's Library edition of his Collected Stories, and oh, what fun they are. Creepy fun, to be sure (I wasn't sure I would be able to continue reading them before bed after a few nights of incalculably strange dreams), but fun nonetheless.
The lesson of this volume is perseverance. The stories are arranged chronologically, and the first ten stories, written during the World War II years, all have to do in some form with aircraft combat or soldiers in exotic places. They're not awful, but they are barely comparable to what follows. Stick with it (or skip the first 150 pages). Beginning with the eleventh story, "Nunc Dimittis" (1947) and continuing clear through the very last in the volume, "The Surgeon" (1986), these pieces are Dahl at the very top of his game. Suspense, revenge, satire that bites like a steel trap, and a remarkable ability to hold the punch line and resolution until the very last paragraph, often the very last word.
Everybody gets it in the neck with Dahl - just when they think they've gotten away with something, fate's pendulum swings round and puts things to rights again. From the unscrupulous antiques dealer trying to pull the wool over the eyes of some country yokels ("Parson's Pleasure", which was absolutely painful to read) to the woman who thinks she's managed to create the perfect cover for an illicit acquisition ("Mrs Bixby and the Colonel's Coat") to the young man who belatedly and unfortunately discovers the pleasures of carnivorism ("Pig"), and so on, the bill always comes due.
It's hard to pick favorites from a volume like this, when so many of the stories are so deliciously good, so perfectly paced that the final blow often induces a slight wince for the victim (deserving or otherwise) of Dahl's final twist of the knife. A few particularly cringe-inducing or really absorbing pieces, other than those mentioned in the preceding paragraph, include "Vengeance is Mine Inc." (utterly hilarious), "Taste," "Lamb to the Slaughter" (brilliant), "A Dip in the Pool" (in which our main character is too smart by half) "The Hitchhiker" (delightful) and "The Bookseller" (which is, quite simply, perfect).
A very nice volume, well collected and ably introduced by Jeremy Treglown.