Classic short story collections are a goldmine for that, honestly. I've been revisiting Agatha Christie's 'The Labours of Hercules' lately. Poirot tackles twelve cases, each riffing on a mythological labour, and most are under fifty pages. It's perfect for a commute or before bed—you get a complete puzzle, a clever twist, and the satisfaction of a solution without the commitment of a whole novel.
People often overlook the 'Ellery Queen' short stories, but the early ones from the 1930s are fantastic brainteasers. The language is crisp, the clues are fair, and they have this wonderful 'Challenge to the Reader' break where they dare you to solve it. Modern stuff can get so psychological, which I love too, but sometimes you just want the pure logic of a locked room. I've found the pacing in these older collections is snappier; they don't waste a word.
For something more recent, try Paul Doherty's medieval short story collections, like 'The Demon Archer'. They're historical, obviously, but each tale is a self-contained murder in a monastery or castle, solved by Brother Athelstan. The atmosphere is thick, but the plots are direct. I keep a collection like that on my nightstand for when my brain is too fried for a complex subplot but I still crave that mystery itch.