CARRIE is a terrific book on its own; as a debut, it is simply astonishing. King's first effort does not at all seem the work of a novice. I loved the device of using excerpts from books and articles supposedly written about Carrie White and Prom Night; these chapters give an almost documentary feel to the book. In fact, for some reason, this book reminds me vaguely of HELTER SKELTER, which was, of course, a true story.
Another thing that lends atmosphere to this is King's use of parentheses to show the reader his characters' thoughts and impressions (did he invent this? I can't think of another author who does this), giving the reader a real feeling of identity with the characters.
It is also a very moving book; in addition to being a jolly good horror story, the characters evoke real feelings of sympathy. Carrie's plight is a familiar one; King evokes the middle-class high school pecking order with devastating accuracy, and the story, ultimately, is not only scary, but very sad.
It made a very good movie, incidentally. I recommend both. I've read a lot of Stephen King, but this one is still my favorite.