If you're after good Graham Masterton books try and get hold of his early work (won't be easy). Best bet is probably eBay as these books are long out of print.

The Manitou
Revenge of the Manitou
The Devils of D-Day
The Wells of Hell
Charnel House
The Djinn
Tengu

I found all the books particularly interesting because of their connection with actual legends from different cultures (Red Indian, Japanese, Egyptian etc.) which Masterton had based them on.