Most of what I like mystery-wise is stuff I've seen on PBS
Mystery, although I have had the big book of Sherlock Holmes stories for about as long as I can remember. Others would include:
Colin Dexter's Inspector Morse (modern day).
Margery Allingham's Campion (1920s/1930s).
Peter Lovesey's Sergeant Cribb (Victorian). This is played for a bit more camp than Sherlock Holmes. Cribb is bright but a bit lazy and not at all posh. Constable Thackery is his long-suffering and definitely lower class sidekick. Their detective inspector would send Sherlock straight up the nearest wall. Not too bright doesn't begin to cover it, but he puts on airs because he is a bit higher class. I think my favorite crime scene involved a multi-day "wobble" which is a walking race of the time.
Ellis Peters' Cadfael (medieval Wales). A crusader who returns home to be a monk with some sleuthing on the side. Not bad CSI for the time, either. And then there's the "office politics" in the abbey

.
Ann McMillan's Civil War mysteries which haven't been on TV as far as I know. These might appeal to some here as the protagonist is a white Southern woman who manages to be a pretty good sleuth while more or less staying within the confines of expected behavior for a woman of her class in that time. Of course, she is not above having the help of a free woman of color. You don't need to be a big Civil War enthusiast to understand these books or enjoy them, but a little knowledge of the early years of the war in the East will give you "ahaa" minutes that will increase your enjoyment. As far as I know,
Civil Blood,
Dead March,
Angel Trumpet and
Chickahominy Fever are the only books. I wish there were more.
Nicholas Meyer's (yeah, he went on to do
Star Trek)
The Seven-Percent Solution (Sherlock Holmes meets Sigmund Freud, played for camp).
Jim Lehrer's (PBS Newshour) novel
No Certain Rest ties together a murder during the Battle of Antietam, Civil War reenactors and bad blood in a small New England town.
Michael Kilian's Harrison Raines Civil War mysteries. The author was a long-time Washington, D.C., correspondent for the
Chicago Tribune. His stories follow the adventures of a Secret Service agent. The author has done extensive research on the battles he uses for the backdrop of his cases, some of which (Ball's Bluff and Glorieta Pass come to mind) aren't particularly well known if you aren't into the Civil War.
Oh my! This did get long. Aren't you sorry you asked?