This is a Cthulhu campaign constructed on a very special background. As such it will be very difficult to integrate it into a more 'normal' Cthulhu setup.
This is because the world of Queensguard is mixture of elements from a steampunk scenario (steam engine high tech, magic, but no electricity and/or computers, no areoplanes and no internal combustion engines), a cold war scenario (2 superpower kingdoms fighting with each other, with (northern) america as their main frontier with a 'neutral' zone between the opponents), and aftermath elements (declining knowledge about tech and magic, mostly because of the dualism of the world).
Background and adventure(s) are tightly coupled, with some brilliant ideas. There is some rail-roading involved (and a clever plot for having (nearly) the same showdown at the end independant of what the players undertake).
As consequence, your satisfaction with the adventure will depend on your attidute towards the background. Queensguard is atmospheric dense and convincing. But my feeling is that Cthulhu myth is rather artificial fold into this world.
This is a good campaign for a group looking for an alternative background a bit aside from the well-worn trails.