So let me start with one thing, newsletters are not there to sell your books. Nope, they are not. They are there to give you one more way to connect with your fans and readers and reward them for being awesome.
So, you should let your subscribers know about your book. You should engage them early and often because...by subscribing they have told you they want to be contacted. So don't make them hunt down information about your book. That said, you don't want to turn you mailing list into one big sales pitch. Even though people opt in to your list they don't want an advertisement every time they open your email. It's a delicate balance, but if in doubt ask yourself if you would want to receive that email from an author you enjoy.
Here are the emails I sent out to my newsletter subscribers to create early buzz for Rite of Rejection. Did this help me sell book? I have no earthly idea. But for me, that doesn't matter. I wasn't trying to sell to these folks. Just get them engaged. And I can tell you, that did happen.
This went out a few days before I announced the book release on my blog. I let subscribers know the book would be coming in December and how I would be using the blog to let everyone inside my marketing efforts.
I gave my subscribers a sneak peak of the first chapter (way before it went live on the blog...see benefits). I also invited them to participate in the cover reveal. I didn't do an open ask on the cover reveal. Frankly because I had enough moving pieces without throwing something else into the works. Everyone I reached out to about the blog tour got a cover reveal invite, but that's it. So this was the only way other people.
Free books! I offered everyone on my mailing list a free eBook of Rite of Rejection in exchange for an honest review. That's right. A free book and they got it weeks before release day. The idea here is that they would be among those who could leave a review as soon as the book was available. Some of them even snuck it on to Amazon using the paperback version and surprised me with pre-release reviews. Bonus!
On the day before the book released I send out an email to thank everyone for their support and to remind them to please leave a review. That's also when I let them know they could get a free bonus scene if they emailed me a link to their review.
That's it. Four emails spread out over about six weeks so nothing too crazy that people would start deleting the avalanche of me in their inbox. And every email was focused on something I could give them, be it a sneak peak at information before everyone else, free books or extra content.
This is important: Never once did I ever ask my subscribers to buy the book. Maybe when I'm a little more established this is something I would be okay with. After all, you can't offer a 10K subscriber mailing list a free copy of your book. There is a line somewhere where you gift yourself out of selling books. But keep in mind that I'm focusing on discoverability here. I'm a little baby author in the book world so it's all about getting my name out there.
I'm not suggesting this is the right path for everyone, this is what works for me and so far, it seems to be doing okay.
Oh, and if you would like a free bonus scene from Eric's POV, just send me a quick email with a link to your honest Amazon review and I'll send it to you pronto. :)