Not too long ago we finished The Father Brown Reader as part of our bedtime reading. Nancy Carpentier Brown basically takes a selection of the Father Brown mysteries of G.K. Chesterton (available in the public domain) and lightly redacts them, simplifying the language to make them accessible to kids.
Here’s an interview with Nancy Brown on the Read-Aloud Revival podcast, which has lots of good additional recommendations around GKC:
We really enjoyed the The Father Brown Reader, and I’ve just ordered the follow-up — The Father Brown Reader II. They’re not heavily religious in nature — though they gently hint at Chesterton’s preoccupations with wonder and grace — and they’re not particularly difficult as mysteries either. Perfect, really, for bedtime reading … and a very easy introduction to G.K. Chesterton for the uninitiated.