I'm very happy with the SQL Server Unleashed book. It's a very good book IMHO. Once you become familiar with SQL Server, you might want to get ahold of Ken England's Performance Tuning and Optimizing SQL Server 6.5 book. It goes much deeper into the inner workings of SQL Server 6.5.

If you're looking for a book on ANSI SQL, I like The Practical SQL Handbook by Bowman et al.

And one of my all time favorite SQL books is Joe Celko's SQL for Smarties.

-Mike