Complex sentence: Barrett Willoughby, a.k.a. Florence Barrett, was a best-selling novelist who wrote works of romantic fiction and nonfiction during the 1920s,'30s, and' 40s, mostly set in Alaska, where she spent many years.
Split into simpler sentences: Barrett Willoughby, also known as Florence Barrett, was a best-selling novelist who wrote works of romantic fiction and nonfiction from the 1920s through the 1940s. Her writing was mainly mostly set in Alaska, where she spent many years.