Robert Harris decribes the Villa of the Papyri
There may be lost plays by Sophocles, Euripides and Aeschylus, or even the lost dialogues of Aristotle, as well as a host of other Greek writers. A contemporary copy of Lucretius's poem, On the Nature of Things - which has been recovered - suggests that the villa may yield contemporary copies of Virgil's Aeneid, or copies of Horace, or even Catullus (whose poems have only come down to us in the most tenuous form, via one corrupt medieval manuscript, itself now lost). And it must be possible that a family capable of owning such a villa also possessed a copy of Livy's History of Rome, of which more than 100 of the original 142 books are missing.

In short, in the words of the campaigners (and these are cautious academics, remember): "We can expect to find good contemporary copies of known masterpieces and to recover works lost to humanity for two millennia. A treasure of greater cultural importance can scarcely be imagined."

More here, here and how they managed to read them here