Ok, I realize this is pretty minor, but your proof (on page 4) of two odd numbers always summing to an even number is circular. Do you see why?
"For any integer n, the formula 2n + 1 produces an odd number".
Kind of uses the hypothesis as a given, doesn't it? And later on "This is an even number because 2 times anything is even".
Anyway.... sorry to be petty here, I'm enjoying the book so far, really!
