As a new Booksmart user I just discovered while designing my books that when I print a page proof to test my design (look at type sizes and readability), they do not come out the actual size of the book. In addition, they are not even proportional to the size supposedly being created. For example, in printing a page proof for an 8 x 10" book:
The printed proof is showing a 7.5 x 9.375" page size. Even if I scale this up to 8" for a vertical trim, that would make my page width only 9.33", not the 10" that is listed in your specs. So since the proportions don't match, it is confusing. Is Blurb cutting off some of the page width in its proof set up to allow for space taken up by the binding?
My suggestion would be that it would be most helpful if it was possible to print a proof at 100%, and if some allowance is being deducted from the page size for the area needed for binding, to show that. Would that be possible in the future?
Working in InDesign we can get this kind of accuracy. It would be helpful if Booksmart could also allow accurate page representations to be created during the design process.