I highly recommend the Alex Delaware series. I love it.
Alex Delaware is a literary character created by Jonathan Kellerman. The Alex Delaware detective series begins with When the Bough Breaks, published in 1985. Delaware appears in 27 of Kellerman's popular murder mysteries. Kellerman sets the series in Los Angeles. Delaware is a forensic psychologist; although Kellerman writes a back story in which Delaware practiced as a child psychologist.
Delaware has a friend, Milo Sturgis, who is a gay LAPD detective. Delaware helps Sturgis in his investigations, and the detective who eventually reaches the rank of lieutenant appears in each book in the series. As the series progresses, Delaware's relationship with Robin Castagna evolves, despite two long separations, during which various other romantic interests are introduced.