The proof checklist, front to back
Take the proof to a table with a pen, and nothing else open. No laptop, no phone, no file to compare against. You are checking the object, and the object is the only evidence.
Work in this order. It runs from the outside in, which is also roughly the order of how expensive each fault is to have missed.
The exterior
Look at the cover in daylight. Near a window, not under a ceiling light. This is the color you actually chose, and it will be darker and flatter than the screen version. That is normal.
Then look at it under a lamp. Two light sources, because they will not agree, and warm indoor light does unhelpful things to cream paper and to anything you set in a near-black.
Hold it at arm's length. That is roughly the distance a browsing reader sees it from, and it is much further than the distance you designed it at. Can you read the title without leaning in?
Check the spine is centered. The title should sit in the middle of the strip, evenly between the two folds. A shift of a millimeter is invisible in a file and obvious on a table.
Check nothing has wrapped. No letter of the title creeping around a fold onto the front or back. No part of the author name lost over an edge.
Check the spine reads on a shelf. Stand it upright between two other books and look at it from where a person would stand.
Read the back cover blurb in the hand, at reading distance. Not on screen. Type that looked comfortable at 100% zoom is often a size too small on paper, and reversed pale type on a dark panel fills in as ink spreads.
Look at the barcode block. Clear of artwork and text, and in the position your printer publishes. The block itself is 2 × 1.2 in. If you added a price add-on, check the digits are crisp and unbroken.
Check the finish and the folds. Run a thumb along the four cover folds and look for scuffing or cracking of the laminate, which shows most on dark covers.
The structure
Open the book flat at five or six points — near the front, in both quarters, near the middle, near the end. The middle is the worst case, because that is where the binding pulls hardest.
Look for text curving into the gutter at each of those points. If you have to flatten the spine with your palm to read the innermost words, the inside margin is too narrow for the page count.
Check the first page of several chapters. Same drop from the top of the page, same treatment of the chapter number, same first-line indent rule. Inconsistency here is the most visible amateur tell in an interior.
Confirm chapter openings land where you intended. If you set chapters to start on a right-hand page, every one of them should be on a right-hand page.
Look for blank pages in the wrong place. A blank verso before a right-opening chapter is correct. A blank in the middle of a chapter is a stray page break in the manuscript.
Check the running heads and folios are suppressed where they should be. No running head on a chapter opening page, none on a blank, none in the front matter that is meant to be clean.
In the Interior Formatter. It sets the gutter from your trim size and page count, keeps chapter openings on a consistent drop, suppresses running heads and folios where convention requires, and keeps the final page count even. The proof is where you confirm it in the hand. Start a book → · about the Interior Formatter
The pages themselves
Read three full pages closely. Read them, do not skim. You stopped seeing your own typos on screen somewhere around the fortieth pass, and a change of medium restores them.
Look for widows and orphans. A single line of a paragraph stranded at the top or bottom of a page.
Check word spacing does not jump between lines. One tight line above a gappy one is what a reader feels as "badly set" without being able to say why.
Hold the page at a shallow angle to the light and look for rivers — pale channels of white space running down through several lines. They are far easier to see at an angle than head-on, which is exactly why they survive proofreading on screen.
The details
The title page. Title, subtitle and author spelled and styled as you want them, matching the cover.
The copyright page. Read every line. The ISBN must be the one for this edition and this binding — a paperback and a hardcover are two ISBNs, and a copyright page carrying the other one is the single most common thing found late.
The table of contents. Every chapter title matching the real chapter title word for word, in the right order, with nothing missing at the end.
Images. Sharp at their printed size, placed on the page you intended, the right way round, and not creeping into a margin.
The arithmetic
Count what the book actually ends on and compare it with the number the cover was built for. One number, two files, and they have to agree. If the interior grew after the cover was made, the spine is wrong and everything on it has shifted.
What to do with the marked-up proof
Work through the whole book before you change anything. A half-fixed proof is how books end up at four rounds.
Then make every correction in one pass, re-export both files, and order another proof. If the fixes changed the page count, rebuild the cover before you upload. Nobody treats a second proof as a failure; a run of a thousand copies of a fault you had already found is a different matter.
Make yours
Everything here is built into the tools, and they are free to use: name your book, bring your manuscript or your artwork, and work as long as you like. You only pay when you want the files without the preview watermark.
Next: The proof came back wrong. Now what? · More: Order the proof. Then read it in daylight · Widows, orphans and rivers: the faults readers feel · What belongs on a copyright page · Running heads and page numbers