Think about how you find books online. You scroll a grid of small images, and you stop at the ones that look interesting. Your cover has to work in that moment, at roughly the size of a postage stamp, before anyone reads a word of your description.
Test it small
The simplest rule: shrink your cover to about 100 pixels wide and look at it. Can you still read the title? Can you tell what kind of book it is? If not, the cover needs to be simpler.
What survives the shrink
A readable title. Large, bold letterforms in a strong contrast to the background. Thin, ornate or script fonts often disappear at small sizes, so reserve them for words that do not matter.
One clear focal point. A single strong image or shape reads far better than a collage. Ask what the eye lands on first, and make sure that is the right thing.
Strong contrast. Light on dark or dark on light. Mid-tones against mid-tones turn to mush.
Restrained detail. Fine detail becomes noise. Keep the design bold and let the large shapes do the work.
Genre signals. Colour, typography and imagery tell readers what to expect. A thriller, a memoir and a picture book each have their own visual conventions. Following them tells the right readers they are in the right place. Breaking them tells the wrong readers nothing.
What does not matter at thumbnail size
Spine, back cover, blurb and barcode are invisible in a thumbnail. They matter for print, but they will not sell the book online, so do not let them distract from the front.
Questions to ask your designer
- Can I see the cover at thumbnail size alongside the bestsellers in my genre?
- What are the genre conventions here, and where are we following or breaking them?
- Does the title stay legible in greyscale?
- Will this work as a series, if I write more than one book?
Common thumbnail mistakes
- A title set too small, or in a colour that sits too close to the background.
- Too many elements: a title, a subtitle, a tagline, a quote and a badge all fighting for attention.
- Fine detail that blurs, such as thin outlines, small textures or tiny credits.
- Ignoring the genre. A cover that does not look like it belongs on the shelf can confuse the readers you most want to reach.
How to test it properly
Make three versions of your cover and look at each at about 100 pixels wide, in colour and in greyscale. Ask five people who read your genre which book they would click first, and why. Their answers will tell you more than your own judgement, because you already know what the cover says.
Once the front cover works, plan the back: see what to put on your back cover. If you are deciding between artwork and a photograph, read illustrated cover or photography?
One last check
Put your cover in a row of five or six competing covers and look at them from a distance. Yours should look like it belongs in the row, and still stand out in it.
Our cover design service starts with genre research for this reason: the cover has to fit the shelf and still be noticed on it.
Want to know where your book stands?
Submit your manuscript for a free book review: the whole book, or at least the first three chapters. We'll read it and send you our feedback. There's no obligation.