It is always best to check with your printer before you send them anything. They can tell you which format it is easiest (thus cheapest) to setup for them. The exact dimentions for any type of page, be it a business card up to a map size.

There is allot to concider when doing a book. How many pages it will be, what type of paper and how it is bound affect the size of the page used. For example, 10 pages printed on telephone book type paper will be much thinner than on 110Lb index card stock. The outside sheets have to be wider than the inside sheets to account for the fold. There are just so many pages you can fold into a booket depending on the thickness. Best to double check with your printer before you start throwing all the parts together. That is... if you want a quality product.

keep your color plates limited... Running a full color magazine can bust your budget real quick.