My ds just turned 11. Currently he is enjoying the Vespers vs Cahills series, having recently read the 39 Clues series (Vespers vs Cahills follows on from that).
He loves the HIVE series by Mark Walden and has just moved on to the Earthfall trilogy (don't think the 3rd one is out yet) by the same author.
He also absolutely loves Biggles and has read a lot of them recently. He read the Roman Mysteries last year and thoroughly enjoyed them.
He has also recently read Bear Grylls' series which is aimed at 9+ but has enough content for older children and is very readable.
He does not like fantasy at all but likes adventure books.
Frances Hardinge (A Face like Glass - fantastically written and set underground, another point of fascination for my DS). He's also recently enjoyed Wildwood, which I believe is the first in a series
Absolutely agree that these are great books. My dd loves them. They would not suit my ds as much because of the fantasy element... Gingerly67 has your son read the Mysterious Benedict Society series. They are illustrated by the same person who illustrated the Wildwood series (who I think is the wife of the man who wrote the MBS series). Even better in my opinion!