Good Books on Writing Email and Blog Ad Copy?

I've recently been working towards bringing my site to the next level, and I'm wanting to get into email marketing from lists I build on my site. I've been collecting a list and it's starting to grow from my opt in offer. However I'm just letting it sit right now and not sending emails to it.

What are some good books to learn ad copy and maybe even email list management (when to send, what to send, what to do in lulls between offer cycles etc). An amazing book recommendation on either topic…

Good Books on Writing Email and Blog Ad Copy?