In the collective unconscious, Stephen King is an author of horror novels, simply. This is obviously reducer and it is in "it" as best we discover the extent of his talent. Of course, there are many moments that chill your blood and prevent you from sleep, but above all "it" is for me the most beautiful work that is about friendship. Those who were around them a handful of true friends will recognize in "it" in both childhood passages when heroes are adults. The main thême the novel is really the link that unites the characters and makes them stronger.
Besides this beautiful description of a dream that made America our parents (and who does not emerge unscathed yet) found in "it" all you can look for in a horror novel, emotion and more .
In my reading, there was a before and after "it". And this is King himself who gives us the best summary of his work in his dedication: "The magic is" ...