World Mysteries and Thrillers discussion

My son reads quite a bit. So much so that I am out of suggestions for him. He's gone through all of my kid-friendly suggestions so I am turning to you all for help. He loves mysteries, spy stories, etc. He is currently reading the 39 Clues series and enjoys it very much. Any suggestions would be appreciated. Thank you.

the Young James Bond books by Charlie Higson are quite good fun before he became 007 and was still a wee boy from Scotland.

Sherlock Holmes for kids? Must have read them by now.

My boys and I love the Brixton Brothers mysteries by Mac Burnett.

Frank Peretti has some great kids books with such titles as Door in the Dragon's Throat.

boiled? fried? just kidding

here's a list of classic boy's adventures

Dave Dashaway and His Giant Airship
Dave Dashaway and His Hydroplane
Dave Dashaway Around the World
Kim
The Travels of Jaimie McPheeters
On Jungle Trails
Rikki-Tikki-Tavi
The Mad Scientists' Club: Complete Collection
The Enchanted Castle & Five Children and It
Raffles: The Amateur Cracksman
Arsene Lupin Vol. 1
The Viper of Milan
Trader Horn
She
King Solomon's Mines
The Prisoner of Zenda
The Four Feathers
The Captain From Castile & The Prince of Foxes
Bayonets to Lhasa
Brazilian Adventure
Horatio Hornblower 1 - 11.
Tirant Lo Blanc
Scaramouche
The Coral Island
The Master Of Ballantrae
The Black Arrow
The Lives of a Bengal Lancer
Green Mansions
Beau Geste
Around the World in Eighty Days
The Mysterious Island
Sailing Alone around the World
Man-Eaters of Kumaon
Bring 'Em Back Alive: The Best of Frank Buck
Kim
The Man Who Would Be King
Sir Gawain and the Green Knight
Bomba the Jungle Boy
Bomba the Jungle Boy and the Giant Cataract
Bomba the Jungle Boy in the Abandoned City
Bomba the Jungle Boy at the Moving Mountain
Bomba The Jungle Boy Among the Slaves
Bomba the Jungle Boy on Terror Trail
Bomba the Jungle Boy on Jaguar Island
Bomba The Jungle Boy in The Swamp of Death
Bomba The Jungle Boy The Underground River
Biggles
Parnassus on Wheels
The Haunted Bookshop
Biggles Learns To Fly
Biggles Flies East
Biggles in the Orient
Biggles Defies the Swastika
Biggles of 266
Biggles Goes to War
Biggles of the Camel Squadron
Biggles Fails to Return
Biggles Flies West
The Long Ships

Swallows and Amazons
The Lost World
Quatermass And The Pit
...and there's even a third author I'm thinking of who was a close competitor to Rider Haggard, missing the fame he achieved by a matter of months.. Drat! tip of my tongue!