This year is the 40th anniversary of the groundbreaking horror classic which has enjoyed an incredible resurgence over the past fifteen years or so. A few years ago I was shocked to find this novelization on eBay.
It's a very short read and is based on the original screenplay so certain scenes are slightly different. There is some expanded character development and some brief perspective from Billy's point of view! It's about that time of year again for a visit to the Kappa Gamma house.
This book is pretty hard to find, but it appears on eBay every now and then.