I've been playing Dungeons & Dragons for a very long time. After my best friend when I was a kid introduced me to it, I went on the hunt for books of my own. This was in the late 80s, so there was actually a split between two separate sets of rules. There was Advanced Dungeons & Dragons, and there was Dungeons & Dragons. Two similar, but definitely different, sets of rules. AD&D was the more complex of the two, and was where settings like Forgotten Realms and Dragonlance lived, while D&D used the setting of Mystara and was closer in tone to the original game, to the point of making Dave Arneson's Blackmoor setting an integral part of the history of the world.
I was originally going to get a copy of the AD&D player's guide, which was what my friend had, but was directed to D&D by the bookseller at Waldenbooks. I ended up purchasing the Basic Set and a copy of In Search of Adventure, which collected most of the existing low level adventures released for D&D at the time. That was just the beginning of a long love affair with the Mystara setting and everything connected to it. Over the years I hunted down every publication I could related to Mystara, first buying them new as they came out and later searching eBay for out of print adventure modules and Gazetteers to complete the collection. There are still a very few adventures I don't have copies of, and my copy of the Immortals boxed set is missing the box, but I've very nearly got it all.
With the 5th Edition of Dungeons & Dragons having come out, and looking like a pretty decent set of rules; much more in the vein of 3rd Edition and, yes, classic Dungeons & Dragons than 4th Edition was, I'm feeling the urge to run a game again. If I do, I think it'll be time to revisit Mystara. Maybe I'll finally send a party to meet the cat-people who live on the moon. Not the moon you can see. The invisible one.