A.L.
Is he an animal lover, by any chance? Try the "Cat Who...." books, by Lillian Jackson Braun. They are lightweight crime novels, about a newspaper reporter (Qwill) who solves crimes, and is often inspired by how to find clues by watching his cat (Koko the Siamese). I read them as a teen - a bit formulaic, but the characters are enjoyable. Particularly if you like cats. Start with "The Cat Who Could Read Backwards." Beware, though: the first book was first published in 1966, so there isn't much reference to fancy technology (Qwill won't be calling the CSIs for a DNA test!).