Complex sentence: Dan Ross was a bestselling Canadian novelist who wrote over 300 books in a variety of genres and under a variety of mostly female pseudonyms such as Clarissa Ross, Ann Gilmer, Dan Roberts, and W.E.D. Ross.
Split into simpler sentences: Dan Ross was a bestselling Canadian novelist who wrote over 300 books in a variety of genres and under a variety of mostly female pseudonyms. Other pseudonyms were Clarissa Ross, Ann Gilmer, Dan Roberts, and W.E.D. Ross.