I know the book is not about math (in fact I'm a math major now so I think I know what math is about ;), it was just that the mathy things were the hardest for me. For example understanding the O(log n) algorithm for fibonacci, the square root algorithm, series, exponentiation algorithm, newton's method, etc (especially since I had no idea what a derivative or exponentiation was). I suspect programmers with little math training will have similar difficulties.