Informational Factual Books - These are books about a variety of factual topics such as animals, science, weather, history, etc. Some examples of these books good for boys are Secrets of a Civil War Submarine and Candy Bomber: The Untold Story of the Berlin Airlift's "Chocolate Pilot"
Biography - Books about a real person written by another person. Examples include Leonardo Da Vinci and
Who Was Martin Luther King Jr.?
Autobiography - A story of a real person written by that person. Includes: Through My Eyes and Have Heart: David Eckstein
Action/Adventure - A story in which there is an element of danger and risk. Examples include: The Adventures of Tom Sawyer and Wildfire Run
Fantasy - A story with elements that are impossible. It often involves magic. Some familiar fantasy books are Harry Potter and the Sorcerers Stone and Beyonders
Historical Fiction - A made-up story that takes place in the past. The setting is real, but the characters are fictional. Examples: Al Capone Does My Shirts and A Single Shard.
Horror - Fiction where the events cause dread for both the characters and reader. Examples: The Haunting of Derek Stone and Goosebumps
Mystery - A suspenseful story that involves an event that isn't solved until the end of the book. Examples include Hardy Boys Series and Ravens Gate (The Gatekeepers) by Anthony Horowitz.
Realistic Fiction - A made-up story that could happen in real life. Examples include: Hatchet and Maniac Magee
Science Fiction - A made-up story that involves the use of science and technology. Examples: Ender's Game and Star Wars
Traditional Literature - Stories that are passed from one generation to another and include tall tales, folklore, fables and fairy tales. Examples include: Paul Bunyan and The Ugly Duckling.
Some other terms you might hear that are sub-genres of those listed above, namely science fiction.
Dystopian - Fiction in which the setting is a nightmare world. Examples include: Lord of the Flies and Hunger Games.
Steampunk - World where steam power is still in use. Usually the 19th century and/or Victorian Era. Examples: The Clockwork Three and The Anubis Gates.
Utopian - Fiction in which the setting is the perfect world. Examples include: The Giver