Before you scoff at the teen section of your local book section, shake off any reluctance, because young adult literature had a great run in 2013.
YA novels have well written prose and dynamic characters just like adult lit, and certain titles also include plenty of sex and violence (as evidenced by the fact a book on this list is titled Sex & Violence).
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So add some YA to your reading list. And don't tell the cashier it's for your niece. (They'll know.)