Back matter is a section added after the book content. It's a message from the author to the reader and has a number of purposes.
Let's first cover its formatting - it's exactly the same as you've done for the content so that's done already. Now let's cover what it should contain:
1. First keep the reader's interest. You get one shot at this because as soon as the reader turns the page many read no further. Perhaps you could tell something about how you came to write the book? Perhaps you could outline a follow-up book? Do something to keep their interest.
2. If you've left an impression, now is a good time to ask the reader to leave a review. Remember writing those in school? Most people hate doing them so find a way of giving the reader guidance. Author Cathy Astolfo gave some excellent guidance on review writing. In her words:
What I am interested in is your reaction to the novel. This is your opportunity to write two or three sentences (or more) giving your opinion. You are not bound by the old rules. You are relieved of the summary task and you don’t have to prove any expert literary skill to anyone. (Although you may want to demonstrate correct spelling and grammar to be taken seriously.) Your only goal is to tell other readers what you thought and how you felt about this particular book.
3. Have you written other books? This is an ideal place to tell the reader about them and give easy links to where they can buy them. If this is a paper book, use shortened links that are easy to type. I recommend books2read.com links, a domain owned by Draft2Digital which is free and easy to use. For example for my book “Time After Time” I created the link https://books2read.com/tat which points the reader to lots of e-retailers and also automatically adds the appropriate affiliate link.
4. Give the reader an opportunity to join a mailing list or visit a website about the book.
Example: Here's the back matter for that “Time After Time” book:
Next step: Adding headers and footers to your book; you won't need these for ebooks but deleting them before making an ebook is a quick and simple task.
Curiously, as I said, I wrote these stories starting in 2015, the fourth being written in 2023. This year, 2024 I read a copy of Ray Kurzweil's 'The Singularity is Near' and realised the timebots I proposed in these short stories were much the same as the nanobots proposed in Kurzweil's singularity.
As an Amazon Associate, I earn from qualifying purchases.