I've been reading Harry Potter in Ancient Greek recently.
I had started it quite a while ago, but found it slow going, since this was pretty different from Modern Greek—not even as close as, say, NT Koine.
However, a while ago, I picked up the Modern Greek translation of the first book and read that through; that went pretty quickly, and I found to my satisfaction that I understood almost everything, except for the specialised vocabulary (cauldrons, rats, spells, etc.), though I could usually understand those words from the context, too.
Now that I recently read that, I resumed my reading of the Ancient Greek translation and found that it helped a little bit.
Coming home from work this afternoon, I overheard a couple speak Greek to their children, and thought it was good that they're passing on their language. I considered telling them that, but the first that came into my mind was Ως ευ ποιείτε ομιλόντος αυτοίς ελληνιστί—I guess I had had too much Ancient Greek recently! (Though the αυτοί in there is a modernism.) I wonder whether they would have understood it.
I tried to think what that might be in Modern Greek and came up with Καλά κάνετε με το να τους μιλάτε στα ελληνικά; when I was about to get off, I thought of Καλά κάνετε που τους μιλάτε στα ελληνικά, which is probably better style.
Incidentally, I was a bit disappointed with the Modern Greek translation in spots. For example, that they called the Quidditch balls simply "the black one, the red ones, the golden one". And I'm not sure where they came up with the house name "Hufflepuffle". The worst was the mirror of "Erized", though, and its inscription Έριζεντ στρα ερόι όιτ ούμπε κάφρου όιτ ον βόζι Erized stra eroy oyt ube cafru oyt on vozi, which makes about as much sense as if it had been Aimythipe nitus said raksi tal lausop osor poton chiedned in the English copy of the book. (And I wonder whether ερόι eroy was a typo for ερού eru.)