Eugene Tyson said:
Set up a new document.
If the book is 210 (w) x 297 (h) mm, for example.
You want to insert the width for the new document to be 210 + 210 + Spine Width
So if your spine width is 10 mm then your cover size is 210 + 210 + 10 = 430
At this point I usually give the cover 2 columns and make the gutter 10mm (the width of the spine) and this gives me a visual grid using the guides.
Front cover goes on the right
Back cover goes ont he left
Spine goes in the middle.
For the spine Text, draw a text frame that is 10 mm in height.
Insert your text.
Rotate the frame so that the top of the letters face the front cover, and the bottom of the letters face the back cover.
Place the text frame in the Spine Area – adjust the position so that the text is visually centered on the Spine (in CS4 you can rotate the page view via the Pages Panel to make it easier)
Once you have this done, make sure your document bleeds the correct amount off all sides.
Then you're done.
If you have anything going on the inside of the cover, insert a new page, and
put the Inside Front Cover to the left hand side
put the inside back cover on the right hand side
Leave the Spine Area on the inside free of ink, as if there is ink on the inside of the spine the glue won't stick to the book.