To Play the Fool is the second book in Laurie R. King's Kate Martinelli series.
Kate Martinelli is a police inspector in the San Francisco Police Department. (The police department's site is great - they show pictures of the officers in different locations - on horses in Golden Gate Park, on motorcycles with the bay in the background, on bicycles with Golden Gate Bridge in the background... what a beautiful place to be a cop!)
In the first book in the series, A Grave Talent, we met Kate's life-partner, Lee Cooper, and her work-partner, Alonzo (Al) Hawkin. Lee was shot in the back and paralized by the bad-guy in the first book, and is now dealing with recovering from that event.
Kate is having to deal with the normal (or extreme) stresses normal to police work, as well as (a) being "outed" very publicly, fighting for domestic partnership rights in the police department, and with the extraordinary stress of having a family member recovering from paralysis.
I love this series because King introduces a lot of scary concepts - homosexuality, homelessness, disabilities, and mental illness. She tells me a lot about these topics without getting "in my face", as many "advocates" do. At the end, I have a better understanding, more sympathy, and am generally more comfortable.
If you want to get a leg up on the location, King created Kate Martinelli's World. It's a great introduction to the San Francisco area, and will give you a head start when you begin the book.