Avid readers know a lot of unfamiliar words but often don't know how to pronounce them because they read them in a book rather than hearing them, because English spelling tends to reflect the developmental history of a word rather than its pronunciation. I mean, if you had never seen the two words "laughter" and "daughter", it is unlikely that you would guess correctly the pronunciation of one, and impossible to guess both correctly, right?
Which is why, if I get a chance to listen to the audio of a book which I suspect holds many unfamiliar words, I read along with it, which also slows down my reading speed and thus adds to the reading pleasure.
Having watched Tom Holland's controversial documentary "Islam - The Untold Story", I was keen to read his book "In the Shadow of the Sword", and was lucky to find both the book and the audio book on the internet.
What a find! What a treat! And I learned how to pronounce "Ctesiphon"!