Slightly off-topic:

When I saw The Keep I thought, “yeah babee!”  Then I read the author & realized you were mentioning a different book.  I might have to pick it up and read it just because of the title (your enthusiasm no less appreciated.) 

For years (& continuing still with every Repairman Jack yarn) I have believed the Adversary Cycle of 5 novels beginning with The Keep and continuing on through all the subsequent Repairman Jack stories by F. Paul Wilson has been the epic idea for this twisted/blessed human existence we all share to one extent or another.  Although the Odd Thomas & Christopher Snow stories by Koontz are very telling about our human epic, the Adversary Cycle, which continues to build to some heady fantasy/reality based climax, is one of the most poignant notions of basic/exceptional good, evil & indifference in fiction [IMHO].   …Just a reflection.