It's a dog's life in the mystery genre. The cats get starring roles, author co-credits, even whole series named after them. The doggie detectives are thrown the scraps. Enter Rachel Alexander, the private eye, who, with her faithful pit bull sidekick, Dashiell, is asked to provide security during a week-long dog training symposium at a posh New York City hotel in "A Hell of a Dog." A former dog trainer herself, Alexander knew the participants, each of whom believed that their philosophy, whether involving the use of prompt and frequent rewards, punishments or reading the pooch's psychic aura, will make them the next Barbara Wodehouse. Her job is complicated by the presence of a now ex-lover who decided to go back to his wife. "A Hell of a Dog" earns its best of show ribbon on several levels. The mystery is suitably mystifying, Alexander is an intelligent heroine with a heart, and the dog handlers are an entertaining pack of purebreeds and mutts. Watching them snapping and snarling at each other is only one of the book's pleasures. Benjamin writes knowledgeably about the dog world and the handlers' discussions and arguments about training are enlightening without being intrusive.