Novel definitely! It has details and certain dialogue/scenes that are not included in the manhwa. For example (spoiler) when Xie Lian actually tricked lan Qian Qiu with combat before Hua Cheng turned him into a doll. You will not be disappointed reading the novel!
Guys I’ve heard lots of great stuff about this series. But should I read the novel first? Or the webtoon? Or it doesn’t matter?