The 2011 editionwas released a while ago (in 2011).
Sometimes the book sells cheaper on Ebay and sometimes it's less on Amazon.
Either way this book is huge. It's the size of most major cities telephone books.
Just got my 11th edition. Be very careful on ordering from Amazon or you will get a old edition, its good but not what you need. The problem is not Amazon but the vendors trying to sell out dated editions as collector books to the unwise. Excellent reference source already planning to buy 3 more for my sons for next CHRISTmas presents.