Moldvay Pink
My parents got it for me for Christmas when I was about 12. I didn't have the slightest idea what D&D was and had never even heard the term before, at that point, I think.
Soaked that up like a sponge. Much easier to digest than the big and separate AD&D books.
For a long time my group used to alternate between Basic/Expert and Advanced campaigns because of the scarcity of modules. Eventually, when more were available, we went to just
1E Adv and later
2E Adv, which I was happy about, because once I got used to Adv, I thought it was vastly superior to B/E.