l0gin's comments

> Authors (actually publishers) use that chapter to list the skills you should have to keep up with the book contents. More often than not, it’s misleading, downplays the expertise you need to have, and it sets the bar unrealistically low.

Opposite is often true for math textbooks. The authors of such texts overhedge unnecessarily, imo.

Open a textbook on, say, differential geometry. The prerequisite are: at least one course of real analysis, facility with linear algebra, knowledge of general topology, some familiarity with complex analysis, bla bla bla. If you are anything like me, upon learning about these prereqs you run off to learn all the ins and outs of nets and filters in topology and end up having studied and finished a textbook on functional analysis. When in reality all that was required for profitable reading of the original textbook on diff. geometry was ability to multiply two matrices together and not up and run in fear when coming across a phrase like "...by compactness argument".

> In my experience the parts of a (study) book where you feel dumb and frustrated while reading are generally the best parts.

True, but not always. Just as often, such parts are terribly written for one or the reason. It's possible that particular section of text is the least favorite of the author so they rush through it. Another possibility is that the author gets tired by the time that section rolls around and just goes thru the motions. Or that the author plain doesn't think a certain section is important enough to expound on it carefully. Yet another possibility is that the author is not universally well-versed in the subject they are writing about: they know some parts better than others.