I've mis-signed many a book Rollins or Clemens. My readers quickly become aware. Booksellers will often promote me under both names, and I do plug both at signings. Generally, the fantasy reader has no problem going into the suspense genre. It's harder for the typical suspense reader to go the other direction.
A true nature is a gloomy monolith, sort of like that old black rotary phone that I had to sing 'Happy Birthday' to Grandpa on. But novelists, damn us, still need true natures - so we can give them to our protagonists. And so readers can vaguely predict how they'll behave when we trap them in 'situations' that they can't IM their way out of.