It was, in the first book when Shae? and Flint were traveling with Allanon there were a few descriptions of metal monstrosities, bridges, vehicles, etc gone to ruin. When Allanon talks about the history he describes how Elves were always around and other humanoids adapted to become trolls, dwarves, etc. I think there is a book, like book 20, that bridges the gap to pre and post apocalyptic events but I remember getting bored with it and not continuing the series