>stories we know of but have been lost from ancient texts
So many there's a lengthy list on Wikipedia about it. It's fascinating reading ancients casually referencing works that we otherwise know nothing else about. Without the careful, laborious copying (often imperfect) over the centuries most things would've been lost completely. There's also other works such as maps that did not survive, the Tabula Peutingeriana for example is thought to be a derivative work of one commissioned by Augustus of the known world at the time (to Romans) and of which there's a few mentions in some works by historians at the time.
A great example about lost work is that the insights we have onto Viking mythology was pretty much documented by a single guy, Snorri Sturluson. What we know about Norse mythology is just a tiny piece of their mythos, as they didn't have the habit of writing down their tales/legends/stories and most of it got lost after they converted to Christianism.
So many there's a lengthy list on Wikipedia about it. It's fascinating reading ancients casually referencing works that we otherwise know nothing else about. Without the careful, laborious copying (often imperfect) over the centuries most things would've been lost completely. There's also other works such as maps that did not survive, the Tabula Peutingeriana for example is thought to be a derivative work of one commissioned by Augustus of the known world at the time (to Romans) and of which there's a few mentions in some works by historians at the time.
https://en.wikipedia.org/wiki/Lost_literary_work