Welcome to the Math Book Notes Wiki[]
The purpose of this wiki is to collect clarifications and errata of math texts. People who are learning a subject for the first time have a different perspective on the material than experts who know the whole subject by heart, and consequently are in a unique position to help each other out. If you've got any books around with the notes you made while you were learning from them, please by all means contribute! The more embarassing the misconceptions, the better -- these are the things that people don't warn each other about, and consequently cause beginning students a massive amount of grief.
Also, I'll try to collect online questions pertaining to texts here, e.g. from math.stackexchange or sci.math.