If you saw the first two films released in 2017 and 2019 and liked the first episode, you'll probably enjoy the series as well.
The first episode is solid, very well developed, and has an excellent ending, which generated a lot of excitement for the entire season.
I love the first series of IT and actually read the book. It was one of the thing that really was spooky and stephen king did a great job in writing them.
I haven't read the book, I've only seen the live-action versions, and the first one made in the 80s is iconic. As a child, I couldn't watch it, but as an adult, I enjoyed it just as much as I did the movies. Maybe someday I'll be motivated to read the book and enjoy King's work even more.