Book formatting software, in the place you wrote the book.

The short definition is that it turns the finished text of a book into the files a store or a printer will accept. In practice that means two files out of one source: a reflowable EPUB for the ebook retailers, and a print-ready PDF at a real trim size, 5x8, 5.25x8 or 6x9, laid out for a printed page rather than a screen. Both have to come from the same text, because the paperback and the ebook are the same book, and a correction that is true in one has to be true in the other.

Underneath that sit the details that decide whether a file passes review. A print interior needs mirrored margins with a gutter, the extra inner margin that keeps text from disappearing into the spine, and the gutter has to grow with page count, because a 400-page paperback opens less flat than a 200-page one. Running heads alternate, author on one side and title on the other, and they drop off chapter openings and front matter. Page numbering starts where the book starts rather than where the file starts.

Typefaces are the other half. Embedding a face in an EPUB or a PDF you sell is a licensing question before it is a technical one, and a good many of the fonts already on your computer are licensed for making documents, not for shipping inside a commercial file. When a formatter offers a font library, it has usually done that clearance for you, which is why the font count appears in every comparison of these tools.

A book is also more than its chapters. Front matter runs half title, title page, copyright page, dedication and sometimes an epigraph or a map. Back matter carries acknowledgments, an author's note, an also-by list and the sample chapter that sells the next book. Each of those has its own page rules, and a tool that only understands chapters will make you argue with it over all of them.

A manuscript is the text plus its structure: chapters in order, scene breaks, italics, the things that carry meaning. Its formatting exists to communicate with a human editor, which is why the convention is double spacing, a 12-point serif and a first-line indent on everything after an opening paragraph. Nothing in that describes a finished page.

A typeset interior is a set of decisions about how the text meets the page: measure and leading, whether a chapter opens with a drop cap or small caps or plain text, how far down the page it opens, what marks a scene break, and how a widow or an orphan gets resolved. None of those decisions changes the text of the book. They decide how the text sits on a page, which is the part a reader notices without naming it.

Confusing the two is where a DOCX-shaped workflow goes wrong. Exporting a manuscript as DOCX and handing it to a print service does produce a printable book; it also produces one that reads as a word-processor document, with a line length built for letter paper, no running heads, and chapters that start wherever the previous one happened to end. Formatting software exists to make that second set of decisions properly, once, and then apply them to every page.

Both answers are defensible, and the dedicated formatters are good at what they do. Vellum is the best known: hand it a finished DOCX and it returns a print interior with very few decisions left to make. It ships 26 typefaces and a small set of book styles, and the small number is deliberate, because there are few enough choices that the book is hard to make ugly. Vellum exports EPUB, MOBI, PDF and DOCX for $249 one-time, and its trial runs unlimited until you want the files out. It runs on macOS and nowhere else.

Atticus is the cross-platform answer at $147. It is a web app that installs as a PWA, so it runs on Windows, Mac, Linux and a Chromebook, and it carries 1,500+ typefaces, print PDF at trim sizes, a chapter list, a focus mode and sync between machines. There is no free trial; the offer is a 30-day money-back window instead. For a writer on Windows who wants a formatter and only a formatter, it is the shortest route to a retailer-ready file.

The other shape is a tool where formatting is a step in the same app the book was drafted in. That is what Calamus is: a Binder, an Outliner, a Corkboard and a Codex for writing the book, and a Compile step on the same file that produces a paginated EPUB, a print PDF at real trim sizes, DOCX and Markdown, with more than 1,900 typefaces licensed for embedding in a book you sell. It is $189 one-time, on Mac, iPad, iPhone and in a browser.

This is the question that separates the two shapes, and it is worth asking before you buy either. With a dedicated formatter, the chain runs manuscript, then DOCX, then formatter, then files. A typo found in the proof means fixing the manuscript, exporting a fresh DOCX, importing it again, and re-applying anything the import did not carry. The tempting shortcut is to fix it in the formatter only, which leaves the manuscript wrong, and the manuscript is what you will open when you write the sequel.

That is one round. Most books go through three or four rounds of proof corrections, plus a title change, plus a back-matter update when the next book gets a release date, plus a second edition. Every one of those rounds is another pass through the chain, and the version you sent to a proofreader and the version you uploaded to a retailer only stay matched for as long as everybody is careful.

When formatting lives in the same app as the draft, the revision is one edit and then Compile again. The trim size, the typefaces, the running heads and the chapter-opener style are saved with the book, so the second compile matches the first without being set up a second time, and so does the third book in the series. There is no DOCX in the middle, which means there is no correction that has to happen in two places.

Compile reads the Binder, in the order the Binder holds it, and writes out files. Front and back matter are documents in that same tree, so a copyright page or an also-by list is edited where everything else is edited rather than pasted in at the end.

The dedicated formatters are one-time purchases: Vellum $249, Atticus $147. Neither writes the book, so both assume you already own or subscribe to something for the drafting half. Scrivener plus Vellum is $308.99. Scrivener plus Atticus is $206.99. A word processor subscription plus Vellum is a monthly bill plus $249.

Calamus is $189, once, and that price covers the drafting half and the formatting half together, on Mac, iPad, iPhone and in the browser, with updates included. The 14-day trial runs in the browser with no card; during the trial Compile itself is locked, and the files you have written still download, so nothing you type inside the trial is trapped there.

None of that makes a dedicated formatter a bad purchase. The comparison is really about how many programs you want in the path between a finished draft and a file a store will accept.

If you already write happily in Scrivener, Word or Google Docs and the only missing piece is the interior, Vellum on a Mac is still the shortest path to a beautiful one, and $249 buys a tool you will mostly stop thinking about. Moving to Calamus in that situation means changing where you write, which is a much larger disruption than changing where you format.

If you are on Windows and want a formatter alone, Atticus at $147 is the cheaper and more direct answer, and it runs on the machine you own. Calamus runs in a browser on Windows and that works well, but the native apps are Mac, iPad and iPhone, and it is fair to weigh that.

If you format other people's books and clients ask for Vellum by name, keep it. The writer this page is for is the one buying a drafting tool and a formatter separately, and carrying a DOCX between them on every revision.