I also recommend reading Gary Taubes' Why We Get Fat: http://www.amazon.com/Why-We-Get-Fat-About/dp/0307474259
This article will give you a good primer on nutrition with a focus on gaining weight:
http://www.barbellmedicine.com/potpourri/584/
If you have any other specific question I'd be happy to chat through them but HN is probably not the best venue. My contact info is in my profile, I love talking about this stuff so feel free to reach out.