How might one find (or more likely, procure) a list of every book ever written/published? It wouldn't necessarily need to include stuff like Beowulf and the Qur'an.

The Library of Congress is probably the biggest library in the world. Their catalog is online, but I don't know if that quite meets your needs.

I want a simple text file of the titles. LOC would be good, as would Amazon.

You'll have to try asking them if such a file exists. I doubt it and if it does, it is probably a few terabytes in size.

LOL.

The Library of Congress catalogue lists every book published in the USA (unless no-one sent them a copy) and those books published abroad which they chose to buy. Obviously there are far more English-language books published outside the USA than inside, and the best general source was the Cumulative Book Index (which unfortunately died in 1999): google to see which bits are available on-line..

LoC for what's published in the USA. British Library for the UK. Other national libraries for other countries. Whether you can actually get the list is another matter.

The LoC has nearly 22 million books. Considering the need to have the title, author, publisher, date, and ISBN, then indeed just the listing will probably be in the terabytes.

You'll probably find you thus cannot get the catalogue because they would not be willing to have someone spend the time to copy it onto several hard drives and mail them to you. Unless you were to pay some hundreds, even thousands, of dollars.

And any such list quite likely WILL include Beowulf, the Qu'ran, and many other old works, all many times over as they will have received multiple editions.

What do you actually want to do? Do you really need a list of every recent publication?