I've bought a box set of the Moomins for DS2 (7) as I had them and loved them as a child. He's also Beano mad so he's also getting the Beano annual and the Official Guide to the Beano. Plus several craft books (especially origami) and puzzle/maze books, and some lego ninjago books that have lego with them too.
DS1 (10) wouldn't give a thank you for most fiction books but adores fact type books - World Records, 1000 Facts about everything, DK Science encylopedia - he sits and reads them for hours and then talks at length about everything amazing he's just discovered. He also loves town planning and maps, so I've got him Jeremy Black's Metropolis: Mapping the City which is more of a coffee table book for grown ups but I think he will love it (and I'll enjoy it too!).
He's also into rugby and football so there'll be books about those too, the DK Geography encyclopedia (although that might go to DH as he often wonders about things he notices around us like the weather or landscape that I learnt in Geography O or A level at school).
They've both got several other books coming that I can't remember right now - will update if I remember what they are!
DH is getting Carol Vordeman's Help Your Kids with Music as he loves music and is learning to play instruments himself, and is trying to encourage the dc to love music too, so I hope this will help all of them. He's getting more but I can't remember what they are off the top of my head.
I've bought a few books for me too for dh to give to me - have been buying way too many books for all of us from The Book People as they have so many enticing books at such good prices. However we have way too many books in the house and are trying to cull them to a more manageable level (let's just say that I've stopped counting books and now count the metres of book shelf plus height of piles of books 
so I'm trying not to buy too many more otherwise we're not going to have any space left to live in the house...