There's no reason to read it "cover to cover", and the GP did not really ask for that. There are many functions in glibc which can be read and understood in relative isolation. I find myself reviewing stable library code (glibc, ncurses, zlib C++ STL) in fits and spurts, several times a year. Sometimes that is paranoia (download the source to make sure the code matches the behavior described in man pages), but mostly it is spelunking to verify something impementation-specific.