Eh, Goodreads has always suffered from the same problem that plagues every other review system which uses "score out of X" ranking. Humans just aren't very good at ranking things on a normal distribution, so you invariably end up with every item (books in this case) being ranked somewhere in the 3.5-4.5 range (since Goodreads is out of 5). For IMDB the rankings all hover around 8ish. When in reality the average book…
It'd be definitely interesting to see a book review site like this. In the meantime, for math books, I trust curated rankings by MAA: https://www.maa.org/press/maa-reviews