And, if I may put my two cents in for a cross-over... let me pose this... F. Paul Wilson teaming up with Dean Koontz. In particular, I mean Dean Koontz's Frankenstein series... it's got all the creepy undertones that could tie in with The Otherness. Not vampiric qualities per se as is the case with Rasalom in the Adversary Cycle, but still the manipulation of man's destiny by a greater being that is immortal yet not indestructible would be an excellent tie-in for a cross-over. Just a thought. Hell, one could also even tie in the Odd Thomas books with the events of A Haunted Air from Repairman Jack.