Out of all of Stephen King's books, this has to be my favourite one. I read this first when it came out, a month after reading "Christine", which I also loved. Leland Gaunt is also my favourite bad guy of all time. I tend to like the bad guys in stories or movies, it's the bad guys that always makes the story so interesting. Without them there would be no conflict and obviously, no story. Gaunt is also very different to King's other villians. While people like Randall Flagg, IT and Tak only want to kill, Gaunt simply wants to be entertained by the carnage and chaos he creates. He'll steal your soul and wreak havoc in the same way we would turn on the computer. He manipulates whole towns for his amusment, like he does with Castle Rock. Now you understand why I like him so much!
Sure, this is a long book and I suggest you only read it when you're sick or on vacation, or in my case, have lots of time while at work.
Also, as with many horror novels, don't read it if you have strong religious beliefs about God and can't tell the difference between scripture and fiction, two totally different things.
I think the point of this book is that everyone has good and bad inside of them. It's connected to desires, needs and interests, but there's more to it than that. Inside everyone there is a struggle, a silent one between good and evil all the time. It doesn't end, that deep down you think you're good but yes, there is a bad part to you, waiting for the chance to emerge. It's just the nature of things, the nature of humans.