I use ConvertKit to manage my subscribers and send newsletters. It is free for up to 1000 subscribers and plans after that start at $29 a month. I love it.
So RIGHT after The End in my new releases, I entice readers to subscribe with a bonus scene. It looks like this (Vellum screenshot):

Notice there is NO chapter to the next book. That’s because I don’t have one yet! I will add that once the next book is on preorder (two weeks before it will release) and then it will look like this:

I still go for the email first! At the end of the sneak peek (chapter one) will be the preorder link.
So when the reader clicks the blue text above they go to a landing page that I created in ConvertKit and embedded in my website. It looks like this on the reader end:

Once they subscribe, they set off an automated sequence. I currently have 12 of these going (I don’t have them for every book, wish I did!) and each has two steps–a form (the signup), which prompts a confirmation email, and a follow-up email. Within my ConvertKit dash, they look like this:

After they sign up, they get a confirmation email that looks like this:

The blue button is linked to a page on my website with the scene.
On my end, setting up that looks like this:

The day AFTER they subscribed they get the follow-up email. The one for CALL ME CRAZY looks like this:

Because I have no next book in the Bellamy Creek Series available yet, I lead them to IRRESISTIBLE. Once BC book 4 releases, I’ll send them there.
For example, the MAKE ME YOURS follow-up email looks like this:

Hope this was helpful!