Diamond Brother Mysteries Books in Order

The Diamond Brother Mysteries are the shorter, snappier side of Horowitz’s detective stories for younger readers. They follow the same chaotic duo, Nick Diamond, a broke private investigator with big confidence, and Tim Diamond, his younger brother who is usually the only one paying attention.

These books are built around one strong hook and a fast run to the finish. A strange client arrives, a simple job is offered, and then the case slides into danger. The humor is constant: Nick misses obvious clues, Tim does the thinking, and the brothers’ bad luck turns every plan into a mess. But underneath the jokes, the mysteries still have real suspects, real motives, and a solution that clicks.

They’re ideal “one sitting” mysteries.

Tim is the detective, Nick just signs the paperwork. Everyone knows it. Even Nick admits it.

The setting is mostly modern London, shown in quick snapshots, a greasy cafe, a cramped office, a back alley, a bus ride that turns into a chase. Horowitz also plays with detective-story clichés on purpose, giving you a hardboiled voice and then puncturing it with a joke. If you’ve ever wanted a mystery that feels like a noir movie and a prank at the same time, that’s the mood.

Titles like I Know What You Did Last Wednesday and The Greek Who Stole Christmas show what the series does well. The setup is instantly clear, the pacing is quick, and the case keeps twisting just enough to stay surprising. The tone stays light even when the stakes rise, because the books are more interested in momentum and banter than in gruesome detail.

You’ll also see the Diamond cases collected in omnibus-style volumes, like Three of Diamonds, Four of Diamonds, and Two of Diamonds. Those collections are useful if you want to read several mysteries back-to-back without hunting down each shorter book. They’re also a nice way to spot which cases you want more of, since the shorter books all have slightly different flavors, blackmail, scams, missing people, or a holiday mystery.

If you’re new to the Diamonds, you can start with The Falcon's Malteser in the main series and then drop into these shorter mysteries whenever you feel like it. If you want something that reads like a funny TV episode with a clean ending, this is the place to begin.