Documents like this (like traditional books) on technical subjects need to be read very carefully, requiring a time commitment that is large relative to the len

Documents like this (like traditional books) on technical subjects need to be read very carefully, requiring a time commitment that is large relative to the length of a human life or career. Also, they have a huge amount of overlap with other similar documents, so critical choices must be made about what to try to read. It would be nice to have a high-quality and widely-used set of community ratings for such documents. E.g. a place where - new documents can be added - they are categorized (automatically should be doable) according to subject matter, level, etc - some sort of community voting system (perhaps augmented by automated scoring by well-established predictors) scores each document for its utility/recommendability, in each of the subject areas that it covers. Does anything like that exist for arXiv? Do people put general expository material on arXiv? (E.g. lecture notes, textbooks, etc).