The linked sources may be variable in their authority and some may require membership, subscriptions, or fees. Nonetheless, gateways often hold good collections of links to explore by category.
Online bookstore locates, describes, and sells books.
Over 2.4 million books available. Info includes title, author, publisher, date, ISBN, cost, and shipping time. Searchable database by author, title, subject, or key word. Good book reviews available on some. Over 1 million books available.