It takes all the best parts of AD&D 1e and marries them to a very specific setting (the titular Hyperborea, which is absolutely more Lankhmar than Tolkien, with a heavy helping of Lovecraft and Thundarr).
If you've been following OSR games for a while but not specifically aware of this one, you may have seen it mentioned under its previous name, Astonishing Swordsmen & Sorcerers of Hyperborea.I was today years old when I learned there was a Hyperborea RPG.