If you're interested, the book Big Fat Surprise talks a great deal about how fat (other than trans fat) isn't bad for you.
http://www.amazon.com/The-Big-Fat-Surprise-Healthy/dp/145162...
http://www.amazon.com/The-Big-Fat-Surprise-Healthy/dp/145162...
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.