These are five books popular over the current teens. As they're easy to understand and don't have much vocabulary, they're a good way to be entertained while learning.
"The Selection" Kiera Cass
The selection is a three-book saga which explains the story of America Singer. She is a normal teen until she's choosen to take part in a contest in which thirty five compete for the heart of the famous and extremely handsome prince Maxon. It is an romantic triology easy to follow. It isn't complex but it has made not readers teens start reading more frequently.
"The perks of being a wallflower" Stephen Chbosky
Charlie is a 15-year-old boy who is coping with the suicide of his best friend. The book consists of the postcards he sends to a stranger explaining his life from the start to the end of his first high school year. He amkes new friends, discovers love, drugs, alcohol, and also has to deal with a family past issue he had repressed.
"The Hunger games" Suzanne Collins
Katniss is a sixteen-year-old who lives in panem, a country in which a Capitol controls all the other districts. Every year two tributes from all the twelve are sent to participate in "the hunger games" where only one person survives. She volunteers to save her sister although she knows she might not make it back alive.
"Divergent" Veronica Roth
The story is set in a place where society is divided into different factions. Every faction reperesents a virtue. Tris Prior has to choose wether she's staying with her family or going away to another faction. She goes through a hard iniciation process which makes her discover a secret she must keep in order to be save and avoid trouble for her family.
"The maze runner" James Dashner
Thomas appears in a big box in the middle of an unknown place. He remembers nothing of his life but his name. In the unknown land there are other boys. Together they will try to escape from the place where they are imprisoned in, which is surrounded by a dangerous maze. They have to overcome lots of problems and fight for their lives which no longer belong to them.