The whole series is formed around the idea of modularity, with the Core Rules as the only really essential book. Based on Core Rules, a referee can run games in any number of genres or settings, simply by adding suitable classes, monsters, spells, treasures, and so on. So far, I've been working on providing the classic fantasy answers to all of these elements (the Classes and Equipment, Cleric and Magic-User Spells, Monsters, and Adventures and Treasures books).
But innumerable alternative books could be used in place of the standards, enabling the easy creation of a rules set for a specific campaign by simply mixing & matching available rules modules. So, for example, you could grab Core Rules + Sword & Planet Classes & Equipment + Lost World Monsters + Planar Adventures & Treasures to make an awesome, dimension-hopping, pulp campaign with laser swords and dinosaurs. (These are largely hypothetical books right now, but you get the idea.)
So that's the concept, and that's where I plan to head with this, once the basic "clone" aspect of the rules are complete. Here are some of the projects that are either in the works or that I have rough notes for. Some of these are being developed by other writers, to be published as rules modules in the B/X Essentials line.
Classic Series (mostly finished now)
- Classes and Equipment
- Cleric and Magic-User Spells
- Adventures and Treasures
- Advanced Characters
- Druid and Illusionist Spells
- Advanced Cleric and Magic-User Spells
- Advanced Monsters
- Advanced Adventures and Treasures
- Lost World Monsters
- Oriental Classes and Equipment
- Oriental Spells
- Oriental Monsters
- Post-Apocalyptic Classes and Equipment
- Character Options
- Biological Magic
- Elemental Magic
- Necromantic Magic
Victorian adventures? Planar monsters? Wild West? Pirates? Science-fantasy? The possibilities are endless!