His three most prolific series were all about detectives and their complex relationships with their loved ones. Spenser - was a former police officer turned private eye; Jesse Stone was an alcoholic detective dealing with a divorce, Sunny Randall was a female investigator.
I enjoyed the Spenser novels tremendously. Spenser was a tough man, a former boxer who was strong, confident and compassionate. He loved to cook, had a foster son, a long term relationship with the woman he loved and a Black best friend. (Spenser:For Hire was also a TV show during the 1980s starring Robert Urich.) He was a very "real" character.
After reading about a dozen of the Spenser books, I stumbled on to the Jesse Stone books. I loved them even more. The Jesse Stone books had less action than the Spenser novels, but they were emotional, complex and intriguing. I loved them.
Robert Parker - a literary great.
Imagine my delight when tv movies were made into the character starring Tom Selleck!