Genealogists who like to relax with a good novel should pick up ``The Port of Missing Men'' by Mary-Ann Tirone Smith, recently issued in paperback by Fawcett Crest (#21891-0, $3.95). While not about the kind of meticulously researched genealogy practiced here, the book is a sensitive portrayal of a young woman's search for her roots that captures the magic genealogists feel when they dig down and uncover interesting ancestors. ``The Port of Missing Men'' is about an Olympics medal-winning diver in the 1920's and 30's. Much of the plot revolves around her and others' quest for ``missing men'' -- fathers, and mothers, grandparents and great granparents in their past. Well-researched and full of period detail, the novel won acclaim from the likes of The New York Times, San Francisco Chronicle, and Publishers Weekly, and is enjoyable on many levels. But it's a special treat for those who seek their roots. We only wish we could have as much fun with as interesting results as does this heroine.