In Japanese shonen manga means "comics for boys". Shonen manga makes up almost one half of all the manga consumed in Japan. Shonen Jump is the best selling weekly manga publication in Japan, selling 3 million copies per week.
Shonen manga are usually full of high action and violence. Comraderie and rivalries are very important to the mostly male cast members. Bromances abound, as do betrayals, and ever stronger foes and allies appear as the plot moves forward. Many of the main characters are motivated by drive to become the best at something--the strongest warrior, the top ranked boxer, the king of the seven seas etc.
Some of the most popular shonen manga are Dragon Ball Z, Bleach, Naruto, One Piece, and Hunter X Hunter, and Slam Dunk.
Dragon Ball Z http://find.minlib.net/iii/encore/record/C__Rb2452986
One Piece http://find.minlib.net/iii/encore/record/C__Rb2268940
Hunter X Hunter http://find.minlib.net/iii/encore/record/C__Rb2317070
Slam Dunk http://find.minlib.net/iii/encore/record/C__Rb2932692