You have to realize that it's not a huge amount of information. The information was produced from the head of an author. You have a pen and paper, and you try to reproduce the results, you read in detail where the stuff gets messy and you couldn't come up with it. The coming up with it is the most important, because eventually you'll be able to come up with 90% of the book yourself, and you are reading quickly, looking for the missing 10%. That missing 10% is the author's crucial insight.
