Ending of Simon Serrailler book 1

[ComeDoonTheStairs]

Hi.
I have just finished book 1 of Susan Hill's Simon Serrailler series. I thought the writing was great. However, I was a bit confused about some parts of the ending:

1. Did they ever actually catch the killer? They were on the hunt for him but don't mention him after a certain point. Or is it a case of being similar to Nicci French, where the killer is not found in book 1?
2. Who was the "you" that was addressed on the tapes? It seemed like the killer had a dysfunctional childhood based on the tapes, but other than that it's not really talked about.

Perhaps some of this is cleared up in future books in the series, or I'm just really missing something. Thank you!

Old thread I know.

Just finished.

The murderer’s body was found hanging from a tree by the woman with the dobermans.

I assumed the tape was to his mother.