A book does not contain anything other than pointers to a group of files that will comprise your book. This is usually used for very long documents that are broken down into chapters.
If you only need a single file then create a new document, not a new book.
I think you have a misunderstanding of InDesign terminology.
A Document is a file you create in ID and save with the .indd file type. It can be anything from an advertisement to a brochure to business card to a custom letterhead to a product catalog to your memoir.
A Book (.indB file) is nothing more than a way to collect a lot of different .indd files together so you can work on them conveniently, and synchronize page numbering and styles.
I suspect waht you want is File > New > Document... and from there you can set up page specs. Once you have a document you can add content to it.
Bob and Peter: Thanks for your replies which fully explain where I am going wrong. Pushed for time, and I didn't give the brain a chance to think it through.
You'd never think I've been using InDesign since CS2, would you?