I'm one of those people who think it looks better if all the numbers are the same, so now I'm wondering if there's any way to raise a pet's specific stat only by one? Also, about books: do they all raise intelligence by 1?

You could try statboosters, which you can find in this Stat Booster List. They're more specific, though far more expensive.

Also, the majority of books give only one AP. There is an exception or two, but I believe it says it in the description.

Thanks!