Sloe Gin is a Brit thing. I'm not aware of people growing Sloes in the US. Sloe Gin is technically a liqueur and ideally homemade.
All I've heard of is a Sloe Gin Fizz. I'd try one and I'm sure I'd like it, but I do not handle booze well anymore other than wine and beer. I do love a gin martini, but...
The protagonist, Dr. Tom More, in Walker Percy's Love in the Ruins was a Sloe Gin Fizz drinker. Like all of Percy's novels, a strong and crazy book.
I know that The Last Gentleman is his most famous book.
Percy, along with Mark Helprin and Cormac McCarthy, are the few contemporary authors for whom I have read everything they have written. True, they are all a bit dark at times.
I like this Amazon intro to Mark Helprin:
Educated at Harvard, Princeton, and Oxford, MARK HELPRIN served in the Israeli army, Israeli Air Force, and British Merchant Navy. He is the author of, among other titles, A Dove of the East and Other Stories, Refiner's Fire, Winter's Tale, and A Soldier of the Great War. He lives in Virginia.