This is the sort of thing that I currently search certain sites for. Like if I'm looking for book recommendations on a certain programming language, I search HN

This is the sort of thing that I currently search certain sites for. Like if I'm looking for book recommendations on a certain programming language, I search HN (eg. site:ycombinator.com rails programming books) I could see this type of thing being really useful. Maybe you could partner with some of the online-learning sites to have the students and teachers rate books that are used for teaching/learning subjects... Good luck with the project!