It's a Kyoto Animation TV series about high school detectives... sort of, sometimes, in a low-key way. The mysteries they solve don't involve murders, kidnappings, etc. but instead just the everyday sort of things you'd see around school. This is based on a novel series, incidentally, and it's a combination of mystery and slice-of-life.
Being Kyoto Animation, it's charming... ish. The main male protagonist isn't interested in being likeable. His name's Houtarou Oreki and he's a miserable git who can't smile. (When he tries, it's unconvincing.) His motto is, "If I don't have to do it, I won't. If I have to do it, I'll make it quick." He can't be bothered with anything. He'd sooner deceive someone than put in effort on their behalf. He even hates the idea of romantic involvement, which sounds like far too much effort, and it's hard to imagine him caring enough even to masturbate. He's not actually rude and he doesn't think his attitude makes him superior to other people, but he's not interested in other people and even his best (only) friend calls him a sloth in human clothing.
Fortunately, though, he's about to meet Eru Chitanda. She's the anti-Houtarou... but that doesn't mean she's a Manic Pixie Dream Girl. She's not a bundle of energy, but instead a complete innocent who tends to get absorbed in things. "It intrigues me!" she'll say, her blue-purple eyes glowing, and you'll hear a magic PING. Whenever this happens, Houtarou is doomed. You can't say "no" to Chitanda. It would be like kicking a puppy. She'll want to investigate, so everyone around her will have to investigate too. (She also tends to invade Houtarou's personal space, which alarms him because it becomes increasingly clear as the series goes on that they find each other attractive.)
She's not stupid, mind you. Naive and airheaded, but definitely not stupid. She's capable of spotting clues and inconsistencies, although Houtarou (to his dismay) happens to be superb at that. This drags him into investigations he'd rather avoid.
Those two are half of the school's Classics Club. The other two are Satoshi (Houtarou's best friend and another anti-Houtarou, believing in having a fun, colourful life) and Mayaka (female, spiky, short-tempered and in love with Satoshi).
It's quite a good mystery series. The low stakes aren't a problem at all. On the contrary, the mysteries are often imaginative and original. There's a story arc about trying to solve a murder mystery... in an incomplete student film, because the filmmakers need to finish the script and they want people to try to work out what the original writer had in mind. I loved the layers in that. It's beautifully animated, with character acting that's subtle and detailed even by Kyoto Animation's high standards. Houtarou's character development is well portrayed, as he goes from being a sour git at the beginning to being ever more infected by Chitanda (even if he'd never admit it to himself).
It's good and worth a look... but it's not my favourite Kyoto Animation anime. Chitanda is adorable, but Houtarou isn't. Obviously. That's the point of his character. K-On!, Love, Chunibyo & Other Delusions, Amagi Brilliant Park and Miss Kobayashi's Dragon Maid can all out-adorable this show and are (for me) more rewatchable, even given Chitanda. That said, though, I did enjoy this and I'll be watching the 2017 live-action film tomorrow.