How do I review my selection and page count before saving?

The selected messages panel shows everything you picked, a live page count, and the Save button that creates your book.

The panel on the right shows every message you have selected, in order, so you can double check before creating the book.

1
"Selected messages" shows your total count, and "Page count" shows a live estimate of the printed pages.
2
Click any message in the panel to scroll it into view in the full conversation.
3
Remove a message from the selection by clicking the X next to it, or use "Clear all" to start over.
4
When you are happy, click "Save" to create your book project and open it in the editor.

The selected messages panel with the page count and Save button

Note: Books can have a maximum of 800 pages. If your selection goes over, trim it down or use the auto split feature to turn one long conversation into multiple volumes.