Hi HN! This app is backed by a graph db containing around 7 million book ratings/affections and 150k book titles published prior to 2020. A query requires at least two books to run and will go about finding books for you based on the collaborative filtering of millions of existing affections. The data used is garnered from a variety of book review websites and open datasets. As well as collaborative filtering it also uses basic criteria like genres to find you matches. Users have found the results to be shockingly accurate so far.