I really enjoyed Hillerman. I must have read at least 6.
Terry Pratchett is my favorite. I think I'm caught up with all of Discworld except for the Wee Free Men series. Most of Pratchett's books are themed. Targets include cops, Australians, banks, the post office, space exploration, etc.
And of course you have Death, dwarves, the four horsemen, witches, vampires, etc.
Back to Hillerman. I classify his stories as 'cultural' detective. In his case it's Native American.
Harry Kemelman wrote an interesting series with a Rabbi as a detective. They turned it into a mini-series called "Lanigan's Rabbi". I think I read most of them.
My guilty pleasure has been
Janet Evanovich's "Stephanie Plum" novels, where the protagonist is a working class Trenton girl who does bail bonds work and solves mysteries. It's sort of a "Sex and the City" meets "Nancy Drew" meets "Jersey Girl" book. I keep on telling myself it's a detective novel, but deep in my heart I know it's one step from Jackie Collins. BTW, if you read them, stick to the books with numbers in the title "Lean Mean Thirteen", etc. She writes these 'between the numbers' novels that move the character into the fantasy realm (working for Cupid, guys who think they're Leprechauns). Pratchett also write some juvenile fiction mixed in his Discworld series (A Hat Full of Sky). If you go in fully informed, some of its not bad. Isaac Asimov also wrote juvenile fiction (Lucky Starr).
Pratchett, Kemelman, and Evanovich are 'fast reads', books you can take to a pool. Hillerman is a little meatier.
Maybe it's generational, but back in the 60's and 70's, you would go to a pool and every other chair would have a 'summer book'. I remember the 'Rabbi' series, 'The Godfather', etc. I just don't seem to see the same number of books out anymore.