Answer by taking a quote from the following article:

James was born in Holton, Kansas; his mother, died in 1954 when he was five. His father was a janitor and a handyman. After four years at the University of Kansas residing at Stephenson Scholarship hall, James joined the Army in 1971. He was the last person in Kansas to be sent to fight in the Vietnam War, although he never saw action there.

An aspiring writer and obsessive fan, James began writing baseball articles after leaving the United States Army in his mid-twenties. Many of his first baseball writings came while he was doing night shifts as a security guard at the Stokely-Van Camp's pork and beans cannery. Unlike most writers, his pieces did not recount games in epic terms or offer insights gleaned from interviews with players. A typical James piece posed a question (e.g., "Which pitchers and catchers allow runners to steal the most bases?"), and then presented data and analysis written in a lively, insightful, and witty style that offered an answer.  Editors considered James's pieces so unusual that few believed them suitable for their readers. In an effort to reach a wider audience, James began self-publishing an annual book titled The Bill James Baseball Abstract beginning in 1977. The first edition, titled 1977 Baseball Abstract: Featuring 18 categories of statistical information that you just can't find anywhere else, presented 68 pages of in-depth statistics compiled from James's study of box scores from the preceding season and was offered for sale through a small advertisement in The Sporting News. Seventy-five people purchased the booklet. The 1978 edition, subtitled The 2nd annual edition of baseball's most informative and imaginative review, sold 250 copies. Beginning in 1979, James wrote an annual preview of the baseball season for Esquire, and continued to do so through 1984.  The first three editions of the Baseball Abstract garnered respect for James's work, including a very favorable review by Daniel Okrent in Sports Illustrated. New annual editions added essays on teams and players. By 1982 sales had increased tenfold, and a media conglomerate agreed to publish and distribute future editions.  While writers had published books about baseball statistics before (most notably Earnshaw Cook's Percentage Baseball, in the 1960s), few had ever reached a mass audience. Attempts to imitate James's work spawned a flood of books and articles that continues to this day.

Did he sell many of them?
By 1982 sales had increased tenfold,