As it so happens I own a copy of the book...
Yes, much of it can be used for a Conan game
Classes: not so much, since it focuses on the core classes and its own classes. The classes presented in the book are very much underpowered in comparison to core D&D, and realy dont belong in a Conan game.
It has its own health/hp system desinged to make combat more deadly, but Conan does it a bit better.
Fear Ratings are perhapse the best aspect of this game that can be ported over to Conan, it give rules for how high to make the FR, as well as a nice list of Quirks and Disorders to inflict... that is to enhance the RP experience of a charcter.
the section on research and investigation doesnt quite fit in with a usual Conan game (how often did we see Conan stop to research a monster weakness before going off to battle it?), still it can be used as a guide for scholars researching a new spell or magical relic.
Like Fear Ratings the section on Black Magic fits well into a Conan game, it provides several "pacts" that a character can make with a daemon or god. these pacts provide a benefit as well as a price (one grants you a +4 profane bonus to bluff and diplomacy checks but requires a will save to avoid using the skill for "destructive, devisive, or otherwise evil manner."
the section on creatures is also easily ported over to Conan, the abomination template is a good way to turn those ordinary Monster Manual creatures into something worthy of REH. and the section on Goddlings is an exelent way to create those creatures that Conan encountered but could never destroy.
the rest of the book is devoted to running a dark fantasy or horror game, and can be of some use to a GM (though not greatly). The adventures in the back could be used as part of a Conan game with some conversion.
