This is a very faithful version of half of the Stephen King novel, telling the story of the kids who encounter Pennywise, a creature that various forms to terrorize and feed on children in the town of Derry every thirty or so years. A few things were changed, such as moving the story from the 50's to the mid 80's, but it works. I keep on hearing a comparison to Netflix's STRANGER THINGS, which is a bit silly, since that whole show seemed to emulate a King story. And the movie also has one of the same actors from that show which furthers the comparison.
But is it scary? Yes, far more than the so-so television adaptation in the early 90's. Bill Skarsgard is creepy as Pennywise. There's something very predatory about the villain and he's always salivating when he taunts any of the kids, as if he can't wait to devour them. The biggest plus is the cast, particularly Sophia Lillis as Beverly Marsh, the lone girl in the group. The special effects are decent, from the first victim having his arm ripped off in a rain gutter to the end scene where we see where everyone "floats".
Hopefully the movie does well enough so that they'll be a part two, with the story continued with the adult characters. Highly recommended, up there with the King adaptations of STAND BY ME, MISERY and DELORES CLAIBORNE.