Mystery vs. Thriller
I've been trying to come up with a satisfying distinction between a "mystery" and a "thriller."
The two ideas I've had are:
1) A "thriller" either tells you who the villain is right away, or there's no way you'd be able to figure it out from the evidence presented.
2) In a "thriller," the characters attempting to unravel the riddle are in danger themselves.
Likewise,
1) A "mystery" give you a set of characters, and the villain is either one of them or someone who is clearly connected to them, and
2) The detective in a "mystery" is able to remain at arms-length from any personal danger.
I'd appreciate any thoughts or insights on the subject.
If the "who and why" are revealed in the last chapter, and there have been no actual clues previously that would direct the reader to the solution, is it still a mystery?
I'm thinking of a specific book in which the person responsible for a series of assaults has a personal grudge against one character, and there is no indication of this person's existence until the final chapter.
The book is well-written and entertaining, but it's classified as a Mystery and I'm thinking that it's more accurately described as a Thriller.
As you have said; "the "who and why" are revealed in the last chapter, and there have been no actual clues previously", ergo you have carried the ‘mystery’ into the theme of the story without early solution. It can therefore be considered to have dominated sufficiently so as to categorise it as a mystery.
My book, The Rod, is about an archaeologist who finds the grave of Moses and comes away with his rod. He soon finds out that it still has the supernatural powers God gave it when he liberated the Israelites. It takes him on the rise to fame and contributes to his death. Afterwards, his possessions are sold at auction and a simple minded, non-religious man buys it not knowing what it is or what it can do. His adventures with the rod takes him on a journey of destruction, even to the brink of his own death.
Now I first called this science fiction-but a couple of agents and writers at the writer's conference that I attend said it was more of a Thriller, so I began submitting it as a Thriller. Then the last agent who reviewed it at a subsequent conference nominated me for the best submission for review (I won $500) and she said not a Thriller but she wasn't sure what to call it.
I think you are right and it is a Thriller. Whatever Dean Koontz's genre is that's what I write.
I vote for "thriller" too.
"Science Fiction" features technological advances. "Fantasy" uses unknown or exotic plants and animals.
In your case, as in the Indiana Jones movies, the source of fearsome power is a holy relic blessed by God.
I'm not sure what Dan Brown's novels are, since in "The Da Vinci Code" we allegedly know where the Grail is hidden, but no one goes after it, and in "The Lost Symbol" the alleged relic is, well, symbolic.
Thank you. You pegged it just right. The difference, I mean. And by the way, I signed a contract with PublishAmerica to have "The Rod" published this year. I'm a little leary about PublishAmerica but so far things are going as expected. I didn't pay them anything, the agreement was acceptible and now the book is in the production stage. Could be out as soon as September. I'll keep a post here. Tell all your friends. I think you'll like it.

Mystery:
A story in which the protagonist (and by default) the reader has to solve unexplained or inexplicable event, phenomenon or plot that arouses curiosity or suspense because of something unknown. Usual they (character & reader) must figure out the ‘who and why’, and sometimes, the ‘how’ during the story … usually the last chapter reveals.
Thriller:
A story usually containing a mix of fear and excitement, sometimes with a spattering of suspense in the mix. Action, adventure and even mystery can be added BUT never in doses large enough alter the genre to any one of these three. It generally has a dark or serious theme, without which it would classify as ‘Drama’ instead of ‘Thriller’.