Unlike with print books, where the margin is bigger on the left or right-hand side of the page depending on which is nearest the spine, eBook margins should be the same on both sides of every page.
We generally recommend that you use .5″ all around. This will ensure that the reader can customize their reading experience without worrying about text loss. When your margins are larger, you risk your book looking like a receipt when it’s displayed on smaller screens.
In some cases margins will be selectable on the device, so the margins you’ve set will be overridden if the reader chooses to do so.
Also, be absolutely sure that all your margins are positive numbers. Negative margins will result in words getting cut off from your book.
[eBook image from Shutterstock.]