What should my gutter margin be?

We recommend that a book's text should have a gutter of 1/2" to 5/8" for ease of reading. However!

For images/artwork going across a spread, we recommend duplicating the images and moving them out from the gutter by 1/8". This will decrease the chance of your image disappearing into the gutter,  but keep in mind it’s not a 100% solution and depends on your page count, binding, etc.