[Stephen King's books have been around for quite a while and I can't really see much of a way to talk about them without giving away plot points and such. So, if you've managed to avoid finding out what happens in his books up to this point and want it to remain that way, I would advise not reading any of my write-ups of his work.] 
Stephen King's first book is pretty short and almost should be called more of a novella than a novel. It however was not the first Stephen King book that I ever read. 
Long before I got around to reading it, I knew the basic plot and what it was about. Girl has telekinetic powers and gets blood dumped on her at the prom, violence ensues. It was hard not to know about that second fact, anyone who saw the cover of the VHS tape or perhaps the movie poster could easily figure that out. I'm not sure how I came about the TK knowledge.
I've never liked reading a book or watching a movie when I know what's gonna happen at the end. So maybe that explains why I put off reading this one for so long. At any rate, when I did finally get around to reading it the first time, I consumed it in practically one sitting. This time around it took slightly longer, but not by much. 
I very much enjoyed it both times. It is a simple straightforward story. Meet the societal outcast. See how the outcast lives. Dump some more on the outcast. The outcast explodes.
There are lots of books that are variations on the theme. Mostly the variations are just what type of outcast we are dealing with and how successful (or not) the resulting explosion is. This one also dabbles in the 'the outcast starts to rejoin society' sideplot as well.
For all of its simplicity it is a very engaging and well told tale. I particularly like how King intersperses the story with news articles, court testimony and other things along the way. I was honestly surprised to find out that he added all of that in the second draft as an attempt to make what was essentially a long short story into a sllightly short novel.
The story about the book goes that when he first sat down to write it, he was so unhappy with it that he threw in the trash and gave up on ot. Only to come home and find his wife had fished it out of the trash, read it the first several pages and pushed him to continue.
Looking at it this time having read the many King books that come after, you can see that the unique Stephen King style and tone are already well developed and present in this book The flow of the story and the characters themselves are very similar to even his most recent stuff.
Perhaps what is most interesting is that for all that the book is a Stephen King type of 'horror' novel, it really isn't a book about the supernatural. Sure Carrie has telekinetic powers and sure she uses them to blow up the town at the end of the book, but the bulk of the novel and the real meat of the story have nothing to do with that. At its heart it is just a story about a girl on the outskirts of societal norms that is pushed beyond the breaking point. The story could be changed to have her lose the TK and instead simply shoot up the town and the message essentially remains unchanged. Perhaps that is why this and many other King books are so successful.
Movie Footnote: I've never seen the original movie made after the book. My understanding is that it is actual pretty decent. Something that can't often be said about the film version of Stephen King works. I believe there was also a more recent remake and if memory serves that one was deemed pretty terrible.
 - Which is a long way of saying, 'spoiler alert'
 - That would be Firestarter, but more on that when I read/grade it.
 - But as I already said, it isn't very long.