Guys love these for the guns and explosions. Women will usually tolerate the violence for the (almost always) male protagonist.
The protagonist uncovers something that someone - or lots of someones - want them to stay out of.
Bad guy is frequently a serial killer. Good guy is frequently a cop or FBI agent.
Someone is trying to destroy the world.
The world is about to self-destruct.
Thriller with lots of sex in between (or during) the action.
At least part of this book does not take place in the present (even if the "past" occurs as distant flashbacks or narrative).
The hero of the story is - huh? A lawyer?
These range from biological terror stories to stories of evil doctors setting out to genetically produce something that should not be.
These have the pace and ticking time bomb of a thriller, but the protagonist also has something to solve. Frequently a crime. Frequently, specifically, a murder.
The government may be in trouble, or they may be the source of the trouble.
The serial killer comes to mind again. The bad guy is often an evil genius who is smarter than the good guy in every way, until the last scene in which the good guy miraculously wises up.
Poor, poor Catholic Church. What has Dan Brown done to you? I'm waiting for someone to write a religious thriller about Krishnas.
Typically two characters fall in love, while one wonders if the other will kill him or her.
NOT to be confused with science fiction, a science thriller features science that is actually possible and realistic in modern times, as opposed to projected science of the future or an alternate world.
Often major overlap with conspiracy and crime thrillers. I guess the only requirement is, there must be a spy.
Any thriller that incorporates something that doesn't really exist on Planet Earth can fall here.
Similar to science thriller, but often more futuristic.
The setting is one of the most important characters in the book. The protagonist might pursue a search that spans the globe, or the entire book might take place in a single village. The trait that makes a travel thriller is that the location must be a location that actually exists.
And now for a fun game. In the comments section below, please list your novel or novels and ALL subgenres they can fall into. I'll start...