Well, in many of the 2015 best mystery thriller novels, complex characters are a common feature. For example, in 'The Girl on the Train', the main character has her own flaws and unreliable memories, which adds to the mystery. Also, unexpected plot twists are abundant. In 'The Martian', just when you think Mark Watney has found a solution, another problem pops up. And in 'Go Set a Watchman', the secrets of the past that are gradually revealed through the characters' interactions are a big part of its charm.
The 2015 best mystery thriller novels often have a sense of urgency. In 'The Martian', Mark Watney is constantly racing against time to survive on Mars, which creates a lot of suspense. 'The Girl on the Train' has a sense of mystery that builds as the main character tries to piece together what she has seen. And many of these novels have a great deal of psychological depth. In 'Go Set a Watchman', the characters' inner thoughts and emotions play a big role in uncovering the secrets of the town.
One characteristic of the 2015 best mystery thriller novels is their ability to keep the reader in suspense. 'The Girl on the Train' does this by having a narrator whose view of events may not be entirely accurate, making the reader constantly question what is really going on. 'The Martian' keeps you on the edge of your seat with the challenges Watney faces on Mars. Another aspect is the exploration of secrets. 'Go Set a Watchman' delves deep into the secrets of a small - town community, both the good and the bad, through the eyes of the returning protagonist.