I'm not selling mine right now--saving them for my twins--but if I were I'd never have thought to post on this board, nor look on it (I only happened to see this because you were the most recent post today so appeared on the list of boards). IMHO his books are pretty heavy intellectually and suited to 6th grade at the EARLIEST. We used them in 7th-8th (history of the world wars) and 9th (economics).