boy writes to pedophile in prision

Nonfiction. Mystery. Takes place in England.
Boy's uncle was killed by pedophile.
Pedophile is serial killer.
Author is female. this is her first book.
written with the last few years.

Blacklands by Belinda Bauer

thanks. you got it right.

And she later wrote Darkside which has the same young boy a bit older - but he's only a fairly minor character. I liked it but not as much as the first as I thought was let down by the somewhat far-fetched ending.