I am looking for a book that develops problem-solving techniques which help develop individual and unique methods to approach mathematics. I find that if I see a problem type I am used to, I do fine in math, but when there is analytic skill required I have trouble finding a solution quickly. Are there any books that help build mathematical techniques opposed to concepts, memorization, and plug-in solutions? Edit: By the way, my skills are developed up to single-variable calculus. Although they are not necessarily refined or perfected.