Book recommendations for 13 year old boy

[PersisFord]

Please help me with book recommendations for my nephew. He was always a completely voracious reader but is struggling to find things that grab his attention but that are reasonably age appropriate. He particularly likes adventure stories, but he's too old for Alex Rider and the like. When I have looked at adult books for him there is a surprising amount of low grade sexual violence which I dont think he needs to read. Same with torture. He also likes fantasy but isn't into romance at all, which is again difficult.

He has read every percy Jackson and the spin offs about a million times
He likes the Skandar books
He liked the Eragorn books
Loved the Hunger Games
Liked the Inheritance Games but they got a bit samey and too much romance
Liked Skulduggery Pleasant
Not keen on Terry Pratchett (i think he is a bit young and the humour doesn't work for him)
Liked Lord of the Rings "ok"

Any thoughts very welcome! He has asked for books for Christmas (just like his auntie!) but I just dont know where to start.

Charlie Higson The Enemy series

@PersisFord - I think we may be twins! So with you on that episode in the Rosemary Sutcliff novel; I was traumatised for about a year after re-reading it in my fifties. And I was poised to say that if you have a bookish nephew the best thing (aside from sharing books) is taking him, as often as you can, to the theatre. (Some of the most blissful moments of my life have been late night post-theatre chats whilst walking back to our hotel with my bookish nephew. Took him to countless things in his city, but it was always particularly fun, when he was young, to introduce him to other cities with a play at the centre of the trip.) I don’t mean children’s stuff; grown up plays, whether freshly written or Shakespeare. Wonderfully, he sometimes noticed things on stage that I hadn’t.)

You don’t mention Susan Cooper, but he may well have read all the Dark is Rising novels already. Another of hers Ghost Hawk is well worth anyone’s time.

If he hasn’t read things like

Erich Kästner’s Emil and the Detectives

or

E. L. Konigsburg’s From the Mixed Up Files of Mrs Basil E. Frankweiler

now might be a good time, before he feels too grown up for them.

Entirely different - the entire oeuvre of Josephine Tey is absolutely unmissable. You wouldn’t think a tween boy would spend a weekend utterly fascinated by

The Franchise Affair

but I’ve seen it with my own eyes! There’s a smidgeon of ‘romance’ in most, but it doesn't get in the way of seriously masterly writing and storytelling.

Three more and then I’ll go away … Interconnected:

Thomas Mallory’s Le Morte d’Arthur (think I read it at around that age).

T. H. White - The Once and Future King (just everything)

and his Goshawk - not about King Arthur!

Pretty much anything here:

https://www.foliosociety.com/uk/fiction

Some fabulous suggestions here. I will try and remember what mine enjoyed at that age but in the meantime I just wanted to say- don't despair! My DS went through a bit of a dry patch around that age but he got back into reading again and hasn't stopped since.
I do remember him liking Holes by Louis Sacher, Lord of the Flies, Animal Farm, To Kill a Mockingbird. He loved Tolkein but I am struggling to think of any other fantasy titles.