Generally I think Robin's readers are under 13 BUT she has ones who've aged up following the series so yeah w a long series that ages up. Oh and AM Dassu's readers are secondary mostly. Not sure about MG.

My daughters are 13 and 14. The younger one is still very much Robin Stevens-level, the older one is reading about serial killers and teenagers disappearing in the woods etc.

We’re big Robin Stevens fans but my kids outgrew them around 12. They would love something like the MMU books (cosy crime, clever, female detectives) but for an older reader. I tried them on Agatha Christie etc but the writing’s a bit challenging/archaic. Though they like Sherlock Holmes… 🤷‍♀️

Sorry I realise that's ambigous, I mean MG leonard, not MG the age range!

I’ve read the MG Leonard/Sam Sedgman train mysteries (which are lovely), and I’d say they’re maybe just a *fraction* younger than Robin Stevens, but there’s not much in it.