The Glain Companion is the expansion Chris Gonnerman wrote for Basic Fantasy when he realized the game doesn't have enough interesting choices for long term play. Basically the same thing Gygax figured out in 1974 when he started writing Greyhawk. And when I say long term play I don't mean one multi-year campaign. I mean several multi-year campaigns. The OSR version of "long term", not the brainrotted 5E player's "long term" meaning 10 sessions.
Gonnerman has a weird line he doesn't want to cross, he doesn't want to produce an Advanced Fantasy to go along with Basic Fantasy in spite of not actually playing capitalist games and therefore technically shouldn't care about competing with himself. But, since Basic Fantasy has reached it's final form by his own admission, really the only obvious next step is finally making Advanced Fantasy. The Glain Companion itself is an admission that it would be necessary for long-term BF players to trade up, as it were, to maintain interest in the system. I recognize he doesn't want bloat, or to demean Basic Fanasy, but the existence of the Glain Companion basically informs the existence of Advanced Fantasy in all but name and proper structure. It already exists, why not make it one book?
Every choice in The Glain Companion is good, except the Bard, but that's because like the Monk, the Bard is fundamentally nonsensical and always has been. Also it's missing a non-raging Barbarian. But otherwise it's a net positive addition to Basic Fantasy, it gives you more options and allows you to more easily integrate AD&D supplements and adventures. The only problem with it is that it really should be integrated into an Advanced Fantasy RPG.
Gavin Norman did something like this for OSE, and his designs are just dreadful. Any design that wasn't strictly done by Moldvay, Cook, or Marsh in an OSE book is hot garbage. OSE Advanced is therefore roughly 2/3 garbage. The difference between these two games is that Basic Fantasy is good, and designed by people who play the game. OSE, like ShadowDark or any of the Mork Borgs, was made to make money first and care about game design second.
