What are some good books that are mystery for kids that are 11+
is Series of Unfortunate Events and the Alex Rider series considered mystery? If so: BEST BOOKS EVER!!!
the Dresden series, for any age 11 plus
nancy drew and Gilda Joyce
The lying game
I loved Judy Bloom books and so did my children.
Stephen Kings book It if you mom and/or dad lets you also the hardy boys would be good even if they are a little old timish
The Hunger Games
John Grisham and James Patterson both write a line of books especially for young readers. I think you would like them.