For those who have not read this book I highly suggest it. I picked up a physical copy at SQL In the City 2012 and could not put it down. Some of it is over my head (it is not a beginner book) but, if you spend a lot of time looking at execution plans (something you should be doing if your job involves writing T-SQL) then this book is a must read.
-- Itzik Ben-Gan 2001