Typesetting quality is the invisible difference
Every tool on this list can put chapters on pages. The differences show in the details readers feel without naming: even word spacing, no lonely last lines at the top of a page, balanced facing pages, and hyphenation that behaves. Vellum built its reputation on exactly this care, and it is the standard any alternative should be measured against.
Coverfairy typesets with the same optimal line-breaking approach used by professional typesetting systems, breaking whole paragraphs at once rather than line by line, and controls widows, orphans, and spread balance. Import your own manuscript and page through the result before paying anything; judge the pages, not the marketing.
Count the real cost per finished book
Unlimited licenses reward volume: at $249.99, Vellum costs about $25 per book across ten books, and Atticus's $147 splits the same way. If you are publishing one or two books, the arithmetic flips: Coverfairy's $19 interior, or $24 with the cover included, keeps the first book's production budget under the cost of most single licenses, and there is no charge until the preview has convinced you.
Kindle Create and Reedsy Studio are free, and honestly useful, with honest limits: Kindle Create locks the book into Amazon's format, and Reedsy Studio trades control for simplicity. Free is the right price for a newsletter magnet; a book you will sell for years deserves whichever paid tool fits your platform and volume.
The cover is half the file, and usually a separate tool
A formatted interior still ships next to a cover: the spine width depends on the final page count, the back cover carries the blurb, and ebook stores show the cover a hundred times more often than page one. Every formatter above except Coverfairy treats that as another program's problem.
Coverfairy is a book studio rather than a formatter: the same project designs the editable cover, typesets the interior, computes the spine from the real page count, renders mockups for launch, and exports every file. That integration, not any single feature, is the honest reason it belongs in this comparison.