This is a bit random, but do publishers like Penguin move a lot of classics each year? Middlemarch’s rank in the Amazon USA list would seem to indicate it sells around ten copies a day. Does that seem reasonable? I thought it seemed a bit low, but my opinion is truly random. There are >12 different paperback editions, so that would seem to argue for popularity…
I was in a big London bookshop a couple of weeks ago and there was a massive table of those Penguin clothbound classics near the entrance, which makes me think they believe people still want to buy classics as Christmas presents at least.