Robert Goolrick's sultry debut novel, A Reliable Wife, has been burning up the paperback charts, blazing hotter than its own early-1900s sex scenes. The book, about a woman who answers a newspaper ad looking for a wife, hit No. 2 on the New York Times best-seller list in its first week. When it was published in hardcover early last year, it got solid reviews and sold a tidy 60,000 copies, but everyone including Goolrick is surprised by its newfound success. ''I had no sense it was going to be this big,'' the author says. ''It's a costume drama with a modern psyche. I think that may be one of the reasons it resonates with people.'' He also credits word of mouth from booksellers, many of whom loved the novel. ''I'm told that the books that sell the most are crime books and romance books, and my book has fallen into both those genres,'' he says. For his follow-up, Goolrick is looking to toss even more into the mix: ''It's going to be about love, adultery, suicide, murder, child abuse, and real estate.''