 However, he has also written some well regarded historical fiction on earlier periods of American history including the American Civil War; early frontier pioneering after the Lewis and Clark Expedition; and the American Revolution.Much of his work has involved series novels typically with continuing characters, although he has written several stand-alone novels as well.A majority of his western novels were written for the established western fictional series of several publishing houses that sometimes used other authors to work on these series, hence the use of "house" pseudonyms for these novels determined by the publisher.