Coloring books
A coloring book is a large, crowded self-publishing category with a tight set of production rules, and almost all of them come from a single fact: somebody is going to put a marker, a pencil or a gel pen on your page. Design for a reader who looks at the book and you will get most of it wrong.
The blank back of the page decides everything else
Markers bleed through print-on-demand stock. Gel pens and water-based pencils soak into it. Even a felt tip shows on the reverse. So a design printed on the back of another design is ruined twice over — once by what comes through from the front, and again if the colorist wants to cut the finished page out.
The category's answer is one design per sheet: art on the recto, and the verso left blank or carrying only something the colorist will not mind losing — a faint pattern, a border, a place to test colors before committing them.
Decide this first, because it doubles the page count and the page count drives everything downstream. Forty designs printed one side is around 80 pages plus front matter, not 40. On KDP's white stock at 0.002252 inches per page that is a spine near 0.18 in rather than 0.09; on cream, at 0.0025, near 0.20. It also crosses a threshold in the other direction: KDP prints spine text only above 79 pages, so the double-sided version of that same book has a spine too thin to put a title on and the single-sided version does not. How to calculate spine width has the rest of the arithmetic.
Line art is not a photograph
- Black line work only. Gray fills are rendered as a halftone screen on a print-on-demand press, which puts a field of dots under whatever the reader lays on top. Keep the art pure black on white and let the reader supply every other value.
- Close the shapes you want colored. A gap in an outline reads as a mistake, and it defeats anyone who colors region by region rather than stroke by stroke. Zoom to the joins before you export.
- Heavy enough to survive printing. A one-pixel line at 300 DPI is 1/300 in, about 0.08 mm, and strokes that thin thicken, thin and break up unpredictably on press. Draw the line weight you want to see rather than the thinnest one that looks crisp on a backlit screen, and keep detail coarser than you think it needs to be — the reader has a marker tip, not a stylus.
- Vector art sidesteps most of this, because it has no fixed resolution and scales to any trim without softening. Vector and raster, and why it matters for a cover applies to interiors too.
Resolution has to be higher than for photographs
Line art is the least forgiving image there is. A photograph hides its pixels in surrounding detail; a long clean curve in black on white does not, and stepped edges along a diagonal are plainly visible at reading distance. Scanned or raster line art is normally captured well above the 300 DPI you would use for a photograph for exactly this reason.
Judge every image at the size it will print, not at the size it opens on your screen. A full-page image on an 8.5 × 11 page needs about 2,550 × 3,300 pixels before you add any bleed. Treat anything under 200 DPI at printed size as a warning and go back for a larger original — you cannot recover a line that was never there.
In the Interior Formatter. Full-page plates, bleed images and two-page spreads are all supported, every image is checked against the size it will actually print at, and the final page count flows to the Cover Maker to compute the spine. Start your interior → · about the Interior Formatter
Nothing important goes near an edge
A design cut off mid-flower does not read as a deliberate crop. It reads as an error, and reviewers say so.
- The trim edge moves. Cutting varies copy to copy, so either keep the whole design comfortably inside the trim, or bleed it deliberately — extend the art 0.125 in past the trim on the outside edges and accept that the outer band of it may be cut away. What does not work is art that stops exactly at the trim line.
- The gutter swallows the inner edge. In a perfect bound book the inside of the page curves into the glue, and that is the part of a design a right-handed colorist reaches last. The total inside margin goes up in steps with page count: up to 300 pages, 0.5 in; 301–500, 0.625; 501–700, 0.75. Remember that single-sided printing is what pushes you across those steps — 160 designs is a 320-page book, and a wider gutter.
- A frame is the easy fix. Setting the art inside a ruled or implied border means the trim tolerance eats white space instead of drawing.
Trim size and binding
Bigger is better here. A coloring page is a working surface, and a larger one holds more detail at a size a marker can hit. That runs against the usual trim logic, where a smaller page is cheaper on every copy, so decide by what the art needs and cost it afterwards. Choosing a trim size covers the trade.
Lying flat matters as much as size. A perfect bound book fights the hand holding it open, and colorists respond by cracking the spine flat, which eventually sheds pages. Coil and wire-o bindings solve it outright where your printer offers them — see Books that need to lie flat. If perfect bound is all you have, widen the inside margin beyond the floor and keep the fold empty.
Take the heaviest paper your printer offers, and test the proof with the medium your reader will use rather than the one you have on your desk. Paper weight, opacity and show-through explains what you are buying.
The honest part about this market
The category is saturated, and it does not compete on the quality of the art inside. Buyers choose from a thumbnail and a theme — a specific subject, a named style, a defined audience — and almost none of them see an interior page before they buy. That is an argument for spending real effort on the cover and on picking a theme narrow enough to be findable, not an argument against making the book.
Typeset your book
The Interior Formatter is free to use: name your book, bring your manuscript, and it sets real pages you can read before you commit to anything. You only pay when you want the files without the preview watermark.
Next: Books that need to lie flat · More: Margins and gutters · Putting images inside a book · Color inside the book, and what it costs