Unless your lad is doing what I used to do, and spending half the night reading by torclight in bed, I'd say he did a fair bit of skimming :-)
So, s few more authors you might want to have a look at.
Michael Morpurgo - very good stories, well written, and sometimes based on fact.
Terry Pratchett has written some books for younger readers - very quirky sense of humour, but again good stories, and to be honest, I'd say even the Discworld series would be suitable, though he's probably miss a lot of the humour.
Roald Dahl. hmmm ... To be honest I don't actually like his books, but my youngest lass really enjoyed a lot of them (the oldest one isn't much of a reader, more's the pity).
John Wyndham - specifically Chocky which would be suitable for his age, and is sci-fi. Others by him, Day of the Triffids, The Chrysalids, The Midwich Cuckoos aren't really suitable for his age.
If he enjoys a bit of fantasy and sci-fi, Ursula Le Guin has written some books aimed at younger readers. I can't comment on them as I've never read them myself.
Finally, and very classic now, how about the Narnia books ? Yes, there is a religious bias in them, and he may not like the writing style very much, but one never knows.
It may also be worth keeping an eye on the schedules for BBC Radio 7 (
http://www.bbc.co.uk/radio7/). They have broadcast adaptations of several Terry Pratchett books (look at the sci-fi stuff which is broadcast at 6pm), some of Wyndham's books, Pullman's His Dark Materials trilogy, as well as a couple of John Masefield's books for children (The Box of Delights springs to mind). Also check out the weekend broadcasts, especially during the main school holidays where they sometimes have radio adaptations specifically aimed at children.
Now, that should keep yhim (and yo