Grown-up science fiction for almost 11 year old

He absolutely has to read this book, This Star Shall Abide. I read it when I was about his age and it has stayed with me ever since. It's part of a trilogy, but I think it works better as a stand alone book.

Space Captain Smith, by Toby Frost.
Tales of the Ketyy Jay by Chris Wooding. CW has also written a series which starts with Malice, which are scifi-ish.

I've just re-read the Tripods trilogy as it came out on Kindle a few weeks ago, and it stands up pretty well after all these years. It is a teeny bit sexist in as much as all the main characters are boys, but as the population has been reduced to a fraction of it's original numbers and is society is functioning in the way that it did in the middle ages it sort of makes sense that girls are more circumscribed in their movements.

Alastair Reynolds might be a good one for him in a couple of years. There's little or no sex but some gore and fighting and some of the books are huge so a big commitment to read. The Prefect might be a good one to start with, or Diamond Dogs, Turquoise Days.

Great suggestions ^^

Another I read at that sort of age was City by Simak. Far future, dogs and robots. That book stayed in my head forever.

Found old copies of Jurassic Park and The Lost World, and DS (11) got hooked on instantly!!! He was all praises, loved it more than the movie and got me reading them again!

I started off reading Piers Anthony , particulary his Xanth series, and also the Incarnations of Immortality series, but tbh they're more fantasy than anything else. I'm trying hard to think of ones that weren't a wee bit dodgy (I was an avid Heinlein reader, but maybe not the ones I should have been reading at that age. Ditto Philip Jose Farmer) A good space based one was the Sector General series by James White - sort of like ER in space but with really weird aliens and lots of science.

Philip Reeve - the series about the moving cities, can't remember the name. My daughter really raved about them. Definitely vote for Terry Prachett - the Disc world and he has a series aimd at 10-12 yr olds. for girls the series about the girl witch Tiffany although the wee free men would also appeal to boys

Dh says most of HG Wells, and I second Takver's mention of Jules Verne.

There's also dystopian stuff like 1984 and Animal Farm he might enjoy.

The Midwich Cuckoos is rather good and quite scary.

Anything by Terry Pratchett he's sure to like- there's nothing age inappropriate afair.

Just came across an old copy of HG Wells stories today, might he like the Time Machine? Ditto Jules Verne, still fun - perhaps even more so because of the dated-ness

I'm sure it would be very educational, volestair

Good point about the Chrisalids vs Triffids - I have to say dd did really liked the Triffids anyway, it was only me who it drove round the bend.

Heinlein's excellent for the "juvenile" novels. These are:
Rocket Ship Galileo (not so great, this one)
Space Cadet
Red Planet
Farmer in the Sky
Between Planets
The Rolling Stones
Starman Jones
The Star Beast
Tunnel in the Sky
Time for the Stars
Citizen of the Galaxy
Have Space Suit--Will Travel
Podkayne of Mars

These stories are all completely absorbing for young kids. They also teach quite a bit of science. The mores reflect liberal America of the 50s/60s, but in a generally good way, and women characters are often smart and competent (eg Podkayne). It's interesting to see how he introduces ideas that seemed incredibly futuristic at the time of writing in a very naturalistic way, and how some of those ideas now have come true, eg the scene at the start of Space Cadet involving a mobile phone (Space Cadet was written in the 50s).

There are some Heinlein short stories that are really good, too. And while there's odd stuff in many of the later books, a few of them are also very good (I always liked Friday, for example).

I think the cut-off date for Heinlein is anything published after 1961 (Stranger In A Strange Land).

Asimov I think is universally age-appropriate, as is Clarke.

What about Bradbury - I haven't read The Martian Chronicles in ages but it should be OK?

James Blish Cities In Flight?

There's just a little bit too much sex in Niven I think.

If he just wants to read a lot of sf then there are enormous numbers of Doctor Who novels, and some of the Star Wars novels are decent enough too.

This is David Brin's list, which is a good starting point, but a few of them are definitely aged 13+, for example the "hero" of The Stars My Destination is a rapist.

I loved Ray Bradbury's short stories at that age.

I loved Heinlein and Andre Norton and read a lot of both from about 10 to 14. Heinlein wrote a whole lot of stuff that is perfect for 11 yr old boys - as well as some stuff that is seriously NOT for children, hence the comment above (stumbled upon one of them at the age of 13 1/2 ...).