I have found many reasons that I wish I had not bought these books. Here are a few: 1) The entire six volume series is written by the same guy who wrote Books Online. In fact, the explanations are identical word for word, so if something is not clear in BOL, these books will do nothing to provide more insight; 2) BOL contains lots more than do these books. To quote the introduction (page 1), "All told, there was about three times as much [BOL] material as there was room in the SQL Server 2000 Reference Library". So the books are an abridged copy of BOL; 3) The books do not appear to include the September 2001 update; 4) The index does not include page numbers, just volume and chapter; 5) The page header on all 1000+ pages of the T-SQL Language Reference says "T-SQL Language Reference" so it's nearly impossible to locate anything and it's useless as a desk reference; 6) It contains the same "Related Topic" links as BOL, but of course you can't click to get there and the index only tells you what chapter to look in. So save your money, or invest it in three or four useful references.