I'm not very familiar with young adult mysteries, but I'm sure they exist. There is definitely lots of young adult romance, which would be easy to read. You might also try Janet Evanovich, an author who writes a lot of romance/mystery combinations for adults. They are lighthearted and repetitive---not high literature but definitely contemporary. Oh, perhaps even more fun would be Ilona Andrew's "Clean Sweep." That's a fantasy mystery with just a tiny bit of romance in it.

Hi Meg, I read a lot ( in Italian :) but I thought or detective story or better classic romance. I try to read The Portrait of Dorian Gray but unfortunatel is too difficult for me... Thanks for your answer

What kinds of books do you like? In general I recommend books written for young adults (YA). They exist in many genres. They are often written in a simple form. Sometimes they are even easier than children's books because children's books have lots of unusual vocabulary (animals, magic terms, fake words). YA books have more everyday language and dialogue.