There are plenty of easy-to-use book formatting options out there for self-publishers these days. And if all you want is a basic formatting solution, it's probably best to go with one of those.
But if you ever hit a point where you want more control over your book formatting, then you're going to want to use a program that gives you control over every paragraph and line and field in your book. And also allows complete control over any image placement and attributes.
When that point comes, Affinity Publisher is one of the best choices on the market. And it's a one-time fee (at least as of June 2022) to purchase.
This book will walk you through how to use Affinity Publisher for both a simple fiction layout with an accent image as well as other more advanced topics such as how to insert tables of contents, indexes, and images.
It combines Affinity Publisher for Fiction Layouts and Affinity Publisher for Non-Fiction, and is part of the larger Affinity Publisher for Self-Publishing series which also covers how to create ad images and basic covers.