If you have photoshop, you have everthing that you need to design and layout a book. All you are paying for when you buy software from someone to layout albums is their templates and a few actions that help make putting the book together a little easier.
If you have photoshop and want something to make the layout process a little easier without spending any $$$ at all, take a look at this site and download the actions and templates:
http://www.fundyphoto.com/free/Downloads.html
They are super simple to use, FREE, and give you the ability to create your own templates as well.
If you are having issues thinking how to make different templates, download a trial of something like You Select it for some ideas. Templates are super easy to build as are albums and you don't need to spend one thin dime more if you already have photoshop.