GenLibriSec is not a relational database in the traditional sense (like a simple MySQL dump). It is a hybrid system.
Researchers use GenLibriSec not to download books, but to study copyright decay. By comparing the deleted_hashes table with DMCA notices, they can empirically measure which publishers are most aggressive (Elsevier and Springer consistently top the list). genlibrusec
Most users never touch GenLibriSec. They use the web front-end. But when they search for "Neural Networks" and see 12,000 results sorted by relevance, that relevance ranking comes from a GenLibriSec query. GenLibriSec is not a relational database in the