I thought I knew how to improve my pics until I read this book. I bought it to learn Lightroom 2, but have learnt so much more. There are many useful tips, tricks and recommended settings to start from. It really has improved my whole workflow, and made a dramitic improvement to my photographs.
It explains everything in a clear and straightforward way. The book is huge though and is a lot to take in, and probably needs more than one reading. I found it best to follow the steps with one of my own pics to see the results on my own work.