John Barnes (born 1957) is an American science fiction author, whose stories often explore questions of individual moral responsibility within a larger social context. Social criticism is woven throughout his plots. The four novels in his Thousand Cultures series pose serious questions about the effects of globalization on isolated societies. Barnes holds a doctorate in theatre and for several years taught in Colorado, where he still lives.
If you want action and adventure in alternate timelines look no further. The characters are just developed enough to be interesting and the alternate timelines are researched enough to be plausible. Not a great work of literature but it does its job and gives you several hours of pure escapism.