Bill Nowlin has authored and edited numerous books for SABR since retiring from the music business, including Puerto Rico and Baseball: 60 Biographies. He has also served as editor-in-chief of the SABR Bio Project. He is one of the most prominent specialist about the history of the Boston Red Sox and has authored numerous books on the subject, in addition to hundreds of biographies of former Red Sox players for the Bio Project. He has been the editor or co-editor of most of the books that have resulted from the Bio Project.
In music, he was the founder of Rounder Records, known for its stable of artists in the American Roots Music tradition. He also founded Rounder Books, which developed a sideline publishing baseball books, including some of Nowlin's own tomes.