Thrillers are a very wide-ranging fiction genre that encompass many subgenres. At its most basic level, it's a story that centers around any drama that isn't a murder. A murder always means mystery, but any other kind of crime or suspenseful drama means it's a thriller.
Action thrillers center around any sort of high-paced, suspenseful plot with lots of action scenes. This is the type of novel that is often made into films and television shows (for example: Jack Reacher, Girl With a Dragon Tattoo, etc.). Try these authors: Lee Child, Stieg Larsson, Joseph Finder, Clive Cussler, Douglas Preston, Lincoln Child, Catherine Coulter, Alexander Soderberg, Nelson DeMille
Romantic suspense novels are contemporary romances that center around the investigation of some sort of crime or some sort of criminal threat. The threat and the investigation serve to bring the two main characters together and add an element of danger. Popular authors in this subgenre are Nora Roberts (sometimes under the pen name J.D. Robb), Sandra Brown, Lisa Jackson, Linda Howard, and Jayne Ann Krentz. You could also put Janet Evanovich in this category, except her novels are more comical and lighthearted, more adventure than suspense.
Techno thrillers center around some sort of technology-related crime or drama. They are sometimes cybercrimes that threaten to take down global networks, dramas having to do with genetic engineering falling into the wrong hands, the invention of some dangerous and mysterious new weapon, etc. Try these authors: Blake Crouch, Tom Clancy, Dan Brown, Michael Crichton
Espionage thrillers always feature some sort of international spy as the protagonist. For example an undercover CIA agent, a spy infiltrating a terrorist organization, etc. The defining characteristic is that the protagonist is a spy and the plot centers around some sort of high-stakes undercover investigation. Try these authors: Len Deighton, Daniel Silva, John le Carré, Chris Pavone, Alex Berenson, Alan Furst
Domestic thrillers focus on the psychological suspense that can happen in domestic settings like the home. They sometimes feature spouses who lie to the other spouse about their identity, family members who go missing, a family member who becomes a threat, or becoming trapped either physically or psychologically. Try these authors: Camilla Lackberg, Lucy Foley, A.J. Finn, B.A. Paris, Greer Hendricks, Gillian Flynn, Paula Hawkins, Ruth Ware, J.P. Delaney, Lisa Jewell, Harlan Coben
Medical and environmental thrillers are closely related to each other. Medical thrillers sometimes overlap with the mystery genre, and often feature a medical examiner or forensic scientist as the main character. Environmental thrillers have to do with some sort of global environmental disaster. A classic example of the latter is Michael Crichton's "Jurassic Park". Novels about global pandemics would be an example of both a medical and environmental thriller. Try these authors: Michael Crichton, Lincoln Child, Barbara Kingsolver, Carl Hiaasen, Robin Cook, Michael Palmer, Daniel Palmer
Military and political thrillers are very closely related to each other. They usually have to do with trying to uncover some sort of terrorist plot or national threat from another country's government. Military thrillers focus on uncovering the threat by a military means, and political thrillers uncover it through the CIA or political means. Try these authors: Tom Clancy, Frederick Forsyth, Brad Taylor, Joel C. Rosenberg, Robert Ludlum, W.E.B. Griffin, Jack Carr, Brad Thor, Vince Flynn, Dale Brown
Legal thrillers always feature a lawyer as the protagonist, and the plot revolves around some sort of high-stakes legal case. Try these authors: John Grisham, Scott Turow, Lisa Scottoline, James Grippando
As the name implies, supernatural thrillers always feature some sort of supernatural element, or the "suggestion" of a supernatural element. The novel might end with the supernatural element being explained as something "natural", but the element of the unknown is what defines these novels. The supernatural element could be anything from ghosts to time travel to the occult. Try these authors: Stephen King, Dean Koontz, Riley Sager, Kay Hooper, Simone St. James, Preston & Child, James Rollins, Alma Katsu
