In reply to pasbury:
I may end up repeatedly posting here as I gradually remember more books, and they'll be more in the area of non fiction rather than just science, but I think they will be relevant:
Various Dorling Kindersley Books (eyewitness guides?) - I remember really enjoying a few of these. I think they also published something called 'The Visual Dictionary' which was my favourite book as a child. Had concise info on everything, from art movements to the anatomy of animals, lots of science and engineering too. That was very well loved that book! Wish I still had one.
Then there were the 'horrible histories' which were good in themselves for history but they had an associated series of science and maths: 'horrible science' and 'murderous maths' which were really good, fun books, I learnt a lot in those. The 'dead famous' series from the same publisher (I think, certainly the same illustrations) were also good. I read and reread the one about Einstien, it was amazing. You almost get a history of modern physics as well as some good understanding into a lot of the actual physics. Again, easy reading, humourous and fun! I think there was a Newton one too which may also be good.
A great history book I think designed for kids in their early teens was 'Written in Blood' by Beverly MacDonald. Quite gory in places, might be worth reading it with him (or reading ahead of him, I think there are some references to genocide, murder, rape etc, may need to be explained) - really is a great book though.
Hope this helps you. Would be interesting to see if these books are still around! Could be worth going and asking in your library too.
Post edited at 22:38