As a child, I greatly enjoyed "Algebra the Easy Way", "Trigonometry the Easy Way", and "Calculus the Easy Way". They present each of the subjects not as already-invented concepts that you just have to learn, but as things being invented by a fictional kingdom as they need them. I greatly prefer that style over rote memorization; I can remember it better when I know how to recreate it. Even more importantly, it encourages the mindset that all of these things were invented, and that other things can be, too.

(Note: the other books in the "Easy Way" series do not follow the same style, and are just ordinary textbooks.)

Also, in a completely different direction, I haven't seen anyone mention Feynman yet, and that will definitely encourage a broader view of mathematics and science.

Or, to go another angle, you might consider things like "Thinking, Fast and Slow".