Like many stories more famous for the movie than the original book, this one’s not quite what you might think.
The 1961 animated movie is actually quite faithful to the plot, though of course streamlined and cute-ified. (Briefly: A young dalmatian couple have a litter of fifteen puppies, and Cruella de Vil, an old school-mate of one of their humans, wants to make dalmatian fur coats. When she can’t buy the puppies, she steals them. The dalmatian parents, assisted by a network of sympathetic dogs, undertake a hazardous cross-country journey and daring rescue.) The only major departure is the car chase at the end of the movie. In the book, the dogs instead get their revenge on Cruella by breaking into her London house and destroying her entire stock of furs.
What makes the book so very different from the movie, though, is a strain of oddity that runs through English kid lit, harking back to Peter Pan (I’ll have a post on that later). Cruella de Vil was expelled from school for drinking ink; she serves blue meat and black ice cream that taste like pepper, and loves excessive heat (hence her obsession with furs); when a puppy bites her, she tastes like pepper. Unlike her comically flamboyant movie counterpart, she has a severely elegant look, and in one illustration looks rather like Morticia Addams. (Throughout the book she wears an “absolutely simple white mink cloak,” which the dogs take delight in destroying at the end.)
Be warned, the female dogs in the book are rather stupid, simply not capable of thinking on the same level as the brainy males. If you’re reading aloud to a child, this can (mostly) be fixed by some judicious skipping and editing on the fly, but it’s tricky. Otherwise, this is an excellent book.