Calculus is a subject that needs to be studied many times over, ideally with a different book in each new round. Using Ezra Pound's analogy (in ABC of Reading), we may think of the learner as an apprentice carpenter, and of calculus as a stool or table; the learner must keep going until the piece of furniture has three legs and will stand up, or four legs and won't tip over too easily. Most people cannot follow this plan, because life is short...