I have finished a photo book with aperture 3.6 but when I try to preview it, the application crashes and I have to force quit so I can't order and buy my book.
Your book may contain a photo or a map that cannot be rendered. You will have to identify the problematic item and to remove it and replace it.
Does the crashlog list the the filename of the photo that is currently processed? Look at the error message, if you are seeing any clue to the problematic photo.
You can also try to identify the problematic item by duplicating the book.
Select the book in the Library Inspector, ctrl-click it, select "Duplicate Book".
Make two copies of the book. From the first copy delete half of the pages, from the second coy the other half of the pages.
Try to preview both copies of the book. If Aperture crashes for one of the copies, the problematic item is in this copy.
Continue by duplicating the copy of the book that keeps crashing and deleting pages, until you found the page that is causing the crash.
Then try to identify the photo or the map on the page that is causing the crash.
Wich version of Aperture are you using? If you are using a version Aperture 3.4.5 or earlier, maps will not work at all any longer.