The Politics of Breastfeeding - do not be put off by the title: it is fab, inspiring, informative and confidence inspiring. I really wish I'd read it before I had DS1. It will also make you angry though...
For practical advice re latching etc I like Dr Jack Newman's website and Kellymom.
The Baby Book by Dr Sears is non-prescriptive and matches my more touchy-feely approach to looking after young babies. A bit annoyingly American though.
Different books/approaches will agree with different people.