Someone Comes to Town, Someone Leaves Town is a truly odd book. It is a mix of hard science fiction and modern fantasy, full of magic that is so inexplicable as to be surrealism and technology that is so mundane as to hardly qualify as fiction. This is the strangest of any Doctorow book I've read, and may actually be the strangest book I've ever read. But it is also quite good.
The story is split between two very different story lines. The first is a rather slow and mundane campaign to set up an anarchic mesh wireless network to provide free wireless internet access for all of Toronto. This is an arduous process of dumpster-diving for old computers to scavenge hardware, and then convincing local business owners to host wifi routers. This is reminiscent of many of Doctorow's other works, including For The Win and Little Brother, although SCtTSLT less groundbreaking and dramatic of the technological front.
The second story line... well, webmaren said it best: the main character is the offspring of a mountain and a washing machine. The tale of his family is a long and odd one, and while the reader slowly becomes accepting of the fact that a family can indeed include appliances and landmasses and other strange things, the inexplicable is never explained. It just so happens that these things exist in the world, and that's that. And, once you get into the book, it's kindov cool. The rather dark and mysterious nature of these magical happenings is quite pleasing once you get over the initial appearance of silliness (this is not a silly book). His fantasy reminds me strongly of James P. Blaylock. although stranger.
There are other, lesser, story lines, all interesting and neatly interwoven. A large part of the story involves the main character's evil brother, who is truly evil, torturing for the fun of it, killing when it pleases him, and generally making his family's life a living hell. Then there are the stories of other characters, including an imaginary one and a supernatural one, but there's no need for spoilers.
Overall, this book is well worth reading. I would like to emphasize that I myself wouldn't be overly excited about hunting down the book after reading these reviews; I don't feel that any review can do the story justice without spoiling the story. I recommend reading it anyway. The writing is a bit unpredictable at times, and to some extent this includes the first chapter. The book starts out... almost boring. If you find the start of the book uninteresting, push through, it gets more interesting. If you find the main character boring and patronizing, keep reading, he develops nicely.
Best of all, the book is free, released by the author under the Creative Commons license. You can download it in any number of formats here, read it on-line here, or even download the podcast here.