How to get the book
The book can be purchased from the publisher, No Starch Press; via Amazon.com; or ordered from any fine independent bookstore. The paper version features a detailed layout and index and lay-flat binding.
A note on other sites
The webpage for the book was originally at http://howwikipediaworks.com; unfortunately, the domain registration of that site expired and was registered by squatters, and it is now no longer affiliated with the authors, although the current registrants are maintaining a copy of the original site. Perhaps they’re fans! However, I would not advise linking there as some of the links are now spam.