In spite of what you may think or what you may hope for, things always change at the very last minute in the preparation of a book for printing.
For example, a new image or new text might need to be inserted or deleted, font or image sizes changed, etc. The problem is that if you develop your book in Photoshop, then when something like this happens, you have to practically start over from square one. Even with a small book, it's a LOT of work.
Instead, you want to use a program like Adobe InDesign which automatically lets text flow smoothly from page to page, repagination occurs automatically, etc. In addition, InDesign comes with many useful templates for books, pamphlets, catalogs, etc., and many more can be found on the web.
InDesign also allows you to specify the binding method that will be used, so that when the book is assembled, the pages will appear in the correct order, even though each one will likely be printed on both sides of a sheet of paper that is roughly double the width of one page. You will drive yourself crazy if you try to do this yourself.
Just my 2 cents.
Tom