Skulduggery Pleasant? Time Riders? Those "George and the Dragon" ones, except I can't for the life of me remember anything else about them - "the last St George" or something like that... Percy Jackson? Mortal Engines? Philip Reeve's "Hungry Cities" series? Jack L Chalker's "Rings of the Master" series? Anything by Douglas Hill Anything (except "The Pendulum Swings") by John Christopher or John Wyndham "Alvin Maker" series or the "Ender" series by Orson Scott Card Anything by H.M Hoover Robert Swindells, but some of his are aimed at younger readers - they're still enjoyable, but more "childish" even to an 11 year old iyswim.
Ds1 who's 11 is currently obsessed with the Robert Muchmore 'Cherub' series - and he's a very fussy almost non-reader most of the time, but is loving them. And there are lots of them so if your ds likes them you've got plenty to go at!
He's almost inconsolable tonight as he's loved the books so much and doesnt believe he'll ever enjoy any books as much again. He's also read Harry Potter, Lauren St John books among others. He recently read a teen John Grisham book and enjoyed that too. I'd welcome any suggestions as to what he could try next.