A TASTE FOR MONEY, by Peter Mars, Commonwealth Publishing, Boston, 1999, 320 pages, paperback, $14.95.

“Write what you know” is good advice that more authors should heed.

Peter Mars follows that guidance. The North Monmouth author spent 12 years as a Boston-area policeman before moving to Maine, where he served as chief of administrative services for the Kennebec County Sheriff’s Department. Not surprisingly, both his first novel, “The Tunnel,” and his new novel, “A Taste for Money” are taut, authentic police procedurals.

While Mars has hinted that “The Tunnel” was based on actual events, “A Taste for Money” is “a novel based on the true story of a dirty Boston cop,” according to its cover. This means he uses the real names of some characters, while in other cases, the names get changed to protect the guilty.

“A Taste for Money” begins with a shooting at Belgrade Lakes, to which Mars and other members of the Kennebec County Sheriff’s Department are called. A wife has just killed her adulterous husband, and, as her story unfolds, Mars and the others find out about a trail of drug trafficking and gun running which involves the deceased and their next-door neighbor, an ex-cop from Boston.

Mars then goes back in time, to tell the story of Joseph O’Fallon (not his real name), who started out well-intentioned but who ended up a corrupt cop who fleeced money from other criminals. O’Fallon narrowly avoided detection for years, despite some conspicuous displays of wealth, and set himself up for a happy, comfortable retirement.

Through interviews with O’Fallon’s friends and acquaintances, Mars is able to take readers inside the increasingly dark soul of the detective gone bad, to help show how O’Fallon became the way he was without ever condoning his behavior.

The problem Mars faces in “A Taste for Money” is that the novel’s lead character is hardly sympathetic and is therefore difficult for readers to either identify with or root for. The rogue cops in “The Tunnel” are working for the good of the community; the rogue cops in “A Taste for Money” are lining their own pockets, building sumptuous homes and buying spacious boats.

Still Mars takes readers on a thrill ride in “A Taste for Money,” as they keep waiting for greedy O’Fallon and company to get their comeuppance. The novel lacks a neat, pat ending, but then, so does life.