Additional I would recommend to use Facing Pages when the document is created, this will not allow to move pages accidently verticaly nor will it allow any space between pages, which could occur with non-facing pages documents.
And of course there's the "old" way, make a single page that is the width of covers and spine combined. I ususally set this up as two column withthe gutter set to the spine width to give me guides, but you don't have to.
The advantage of the 3-page-spread-method is, that it is easier to adjust the size of the spine part when the paper changes or the number of the pages increases or decreases. So it is an easy wasy to set up a template for a series of books and if the editor decides for last minute changes.
Another advantage is to export files from the final front cover files as I have to do in different file types for the publisher's database and advertising without post-exporting cropping process.
Another advantage is when the same book is published in German and Enlish or Spanish. It is so easier to rotate the spine's texts in 180° as the different languages have different directions to read on the spine.
Another of the 3 page spread is that it will create marks where the spine is. Which I absolutely love.
One less thing for me to do - add in Spine Marks to indicate to the prepress where the spine actually is.
I used the 3-page method. Once. I went back to the old way.
It's mostly a matter of preference, and for me the Page tool is such a bundle of horrors that I never use it. It takes only a few moments to adjust the spine and marks when necessary (though you do need to add the fold marks, if you need them). In my experience, though, fold marks are kind of like Walt Disney's Pirate Code -- more of a guide. By the time the covers get to the folder the marks are either already trimmed off, or nobody is looking anyway. The machniery is set up and it's right, or it's wrong, and if there was drift in the cutter, well, that's life.
I love ths tool, but when to use it, there are some limitations:
- Use it onlly as exception. Globally changes should always be done via Document Set Up or New Document, otherwise a wired behavour might occur. (Problems appear later in changing Master Pages.)
- Use it only in facing pages documents, otherwise the pages can move arround on the area.
It is most certainly a matter of preference.
I prefer the 3 page method for another very valid reason.
Making the eBook cover of the 3 page document (or web, or just as a thumbnail for someone) is simply using File>Export>JPEG and choose Page 3 and your image settings.
You can also export just the Cover or Back (or both) to PDF - for sending for review or other uses, like making PNGs for web, or for eBook covers.
I really like the 3 page method - and if you need a flap added (as a dust jacket for example), just add another page.
I've actually used the Pages Tool for creating "folders" with a flap and a gussett.
You can actually move pages to be under one another, basically stacking them.
And selecting "Spreads" keeps them all in the sequence when output.
It's a really powerful tool that I've probably misused. But hey it works for me.