Baby Groot hug Pennywise shirt

I saw the Baby Groot hug Pennywise shirt latest remake, but I watched the original miniseries and then read the book. Stephen King wrote IT so that both parts of the story happened at the same time; The kids first face Pennywise and their adult versions face him a year later. So the book was not spoken sequentially. Both current miniseries and IT films divide the story into two parts. Part one tells the story of the kids facing Pennywise, and then Part Two is the last battle for adults. Therefore, the whole story is told sequentially, instead of past and present taking place at once.