I'm a fan of online novels, so I can't provide any 21st century novels. The 21st century has changed a lot. Many famous books are outdated or no longer popular in the 21st century. However, there were also some very popular novels in the 21st century, such as Game of Thrones, The Three-Body Problem, The Handmaid's Tale, and so on. If you want to know more about these novels, I suggest you search for relevant reviews and reader reviews on the Internet or consult professional novel lovers.