The first product I owned was the D&D Expert Set (Moldvay w/Erol Otus cover). My friend had the Basic Set, and as 8-year-old, we weren't exactly flush with cash. Our group perpetually had the Basic Set checked out of the library that summer until more of us were able to find it. I ended up buying the Mentzer-revision Basic Set several months later, not really understand why mine was the same, but different than my friend's, but I appreciated having the player's stuff and the DM's stuff in separate books.