What I find an interesting 'side topic' is the question how many works that are now lost are actually known to have existed. In some cases author and title are known, but not a single word has survived. In other cases only fragments have survived.
When I first came to Germany, I spent many evenings in a cheap and small hotel room in the attic of a house, and read through "Attic nights" of Aulus Gellius. (Yes, I know this is bad but I could not resist. And it is actually true.)
Anyway, this classical Latin author mentions (among other things) books he has read and what he finds interesting in them, and some of these are now lost. That is just one example.
I remembered the many Greek tragedies that are now lost, and a quick Google provided this easy (and to me fascinating) read:
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