The first book I would suggest is "Small Scale Pig Raising" by Dirk van Loon. He just updated it in 2014. This book has been out for a long time and the first edition was excellent. I expect the update is even better. The first edition which I read was not focused on pasture but covers pigs most excellently.
The second book I would suggest is "Harris on the Hog". This book is about old time pigs and was written long ago. Very good read.
"Swine Science" is more about modern commercial hog raising but well worth reading.
"The Meat We Eat" rounds it out.
You'll also find about 2,000 articles on my blog
http://SugarMtnFarm.com about how our family raises pastured pigs. We have about 400 pigs on pasture and deliver weekly to area stores, restaurants and individuals.
Discussion groups like this one, the Pastured Pigs forum on FaceBook and other places are all good places to go for sharing information and asking questions. Delve into the archives of this group for years of knowledge. If you have a question there is a good chance someone else has already asked that question so the search feature on forums is invaluable.
-Walter