Here is one:
http://ofps.oreilly.com/titles/9781449398583/
and this is how the book will look like once it's out:
http://www.readwriteweb.com/hack/2011/03/nodejs-book.php
Since node.js is still under development, you'll find very few text on it. Still try to look for code/examples on official site and videos are available too if you do a google search.