A manuscript can be carefully edited and still produce a disappointing book file. Formatting introduces a new set of decisions about page breaks, navigation, images, and front matter. Check the actual output after layout rather than assuming the source document tells you how the finished book behaves.
Check the book's identity
Compare the title, subtitle, author name, and edition information across the cover, title page, and listing. Look for leftover working titles in headers and filenames. Verify the table of contents against the final chapter order.
If you include a website or contact address, test it. A printed typo cannot be repaired for copies already in readers' hands.
Examine a physical proof
For print, use the platform's preview tools and inspect a physical proof when available. Look at margins, text near the binding, chapter openings, blank pages, page numbers, and the placement of illustrations. A cover that looks bright on a screen may feel different in print.
Read selected pages near the beginning, middle, and end, then inspect every page visually. Check that captions stay with their images and that a heading has not been stranded at the bottom of a page. Amazon KDP's paperback guide explains its current preparation workflow; confirm the requirements for your chosen platform and book format.
Test the digital edition separately
Try the table of contents, internal links, and sample navigation. Change the font size in a reflowable ebook preview. Check that images remain understandable and that spacing has not been built from repeated blank lines or spaces.
Keep a correction list with the location, the issue, and the action taken. After making changes, generate a fresh output and check those locations again. Approval should refer to a specific final version. Allow time for this cycle in the publication schedule so that proofing becomes a deliberate step rather than a rushed glance before launch.