My first D&D product I ever bought, was the Psionics rule book for 0e. Even though I didn't own the other books, I had heard of the game. As I recall I bought it in a store in Superior, Wisconsin. The D&D books themselves were out of stock, so I picked up this one and then I saw a big soft cover book on the shelf. It advertised itself as a unique role playing game with everything you ever needed in one volume, so I bought Chivalry & Sorcery too.
I know where my copy of C&S is, I think that the Psionics Handbook is in "a box in the basement".
Later - I didn't find that but what I DID find!!! Check back later for that post.