Kids book reccomendations.

I have two kids, age 10 and 12 boys. Mr 10 is a fairly confident reader and will happily read for pleasure, mr 12 prefers graphic novels etc.
I’m on the process of starting to think of festive/birthday gifts for them both, and as the child who always wanted books, I always get them at least one or two each. Or if I find a good deal, a full series.
I’ve just been having a look on Books2door and found the whole Charlie bone collection for £15 which I think mr 10 would really enjoy (I enjoyed what was available of the series at a similar age)
But what series etc to get mr 12, he has all the cat kid and a lot of Dog man, last year he got the full ‘bunny vs monkey’ set, but he is almost 13 and while I know he enjoys graphic novels, I want to maybe find more ‘age appropriate’ ones?

So any reccomendations for a good book series for either of my boys, I would say my 10 year old is probably a more confident reader than my 12 year old, I don’t want to ‘baby’ either of them, but I also don’t want to set them up for failure with something well beyond their abilities.

I’m in the UK bu Amazon exsists. I think I’m looking for ‘middle school’ level books? My youngest is in the equivalent of 5th grade and my eldest I think would be 7th grade in the USA .