I think any novel that doesn't have contentious content or isn't specifically dealing with teen issues can apply. Look at Robin Stevens or maybe MG Leonards', although I haven't read either. Generally, the Rick Riordan, Philip Reeves adventure stuff. Novels, but not issues-driven.

RR and PR are both older so would be interested if they were entering the market now if they'd be made to age down? NOt sure! Mind you I think RR is mostly 11-13 year olds vs 15 year olds.

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.