The Long Tail is an interesting concept and, written in 2006, it perfectly anticipated the new forms of "Me-commerce" as drivem by Google, Amazon, eBay and Netflix.
However, it is somewhat uncanny that Chris Anderson first wrote about the principle of Long Tail in a magazine article: the book is simply too long. While it is arguably a solid theory to discuss commerce in the digital age, Long Tail as a book simply feels convoluted. Anderson clearly makes his point in the first couple of chapter, before going on and on with case studies of a handful of companies (Google, Amazon, eBay, Rhapsody and Netflix).
I would recommend The Long Tail to anyone interested in popular non-fiction, but there is not much information lost if the reader quits after 50 pages.