A couple of fiction writers who use initials are E.L. James, famous for 'Fifty Shades of Grey', and A.A. Milne, the creator of Winnie-the-Pooh. Using initials can add an air of mystery or make their names more memorable.
Well, there are quite a few. For example, C.S. Lewis is one. His fantasy works like 'The Chronicles of Narnia' are popular. Another is P.D. James, known for her crime fiction. These writers chose to use initials for various reasons, maybe for privacy or creating a unique brand.
Some well-known fiction writers who use initials are J.K. Rowling and J.R.R. Tolkien. They have achieved great success with their works.