Having been bored stiff by many a technical book in the past I found this a refreshing read. Having developed for a number of years using T-SQL I would say I was more of a parrot-fashion database developer until I read this book. The knowledge imparted is invaluable and I would definitely recommend it. This is a book mainly for SQL Server 2005 but there are many 2000 samples for replicating the functionality.
Whilst it has a number of early chapters focusing on querying fundamentals I would still suggest this book is for people who have some experience of SQL Server 2000\2005 T-SQL and not beginners. As the chapters progress Itzik starts giving examples of common development problems and then solves them. Two that spring to mind are creating server-side data paging or dealing with hierarchies. The chapters on query tuning really are a treasure trove. I have seen many a developer look at a graphical query plan with an "oooh that looks pretty" face without any knowledge as to its meaning. This will give a good foundation explaining why the little pictures change and what all the cool figures mean!
Itzik also goes into detail about the most important T-SQL language changes and when to use them and when not to. He shows the performance implications of each choice and critically explains them for the mere mortals amongst us (including me).
I find myself reading a paragraph, asking myself a question only to find he has answered it in the next paragraph. A well written book on a difficult subject matter. It is clear that Itzik has a passion for SQL Server and set-based logic and this is apparent in the writing style throughout the book making it an easy read (if your a database guy/gal).