Science fiction (Sci-Fi) typically has story lines that rely on current or imagined future science or technology, and its potential impact on humans. Space travel, time travel, and extraterrestrial life are common elements. Some favorites include:
I Am Number Four by 
Scarlet by 
Steelheart by 
Unwind by 
The New Policeman by 
The Maze Runner by 
Fantasy books often involve magic, superpowers, and supernatural elements. The settings are often rich, imaginary worlds operating outside the laws that normally govern the universe. Magical creatures are common, and the stories often involve journeys or quests. Below are some examples:
Harry Potter and the Sorcerer's Stone by 
The Castle Behind Thorns by 
The Night Gardener by 
Airborn by Books in the mystery genre often have a crime or mysterious situation that needs to be solved. The story involves clues, suspects, detectives and red-herrings, in which the reader is led astray by seemingly important clues that are not really related to the crime. Many mystery books are parts of series.
Below are some examples:
Cross My Heart and Hope to Spy by 
Kid Lawyer by 
The Vanishing Violin by 
The Scandalous Sisterhood of Prickwillow Place by 
Escape from Mr. Lemoncello's Library by