Margins are perhaps the most important part of a book layout. A book page has three margins (outside, top, bottom) and a gutter (the inside margin where the pages are glued or sewed together). Each of those margins has a particular job: the outside margins give room for the reader’s thumbs when they hold the book.
The top margin is where you’ll usually find the author and name of the book, as well as the page number (more on those later!). The bottom margin provides a white space that supports your text block. The gutter makes sure the text doesn’t slip into the glued or sewed area.
we all know the gutter (or inside) margin on bound books has to be larger than the outer margin. The minimum size of the gutter mostly is ¾”(0.75”).
One of the common mistakes in self-formatted books is making these margins too small. As you know, print-on-demand vendors like CreateSpace, Lightning Source, and others base their printing fees on the number of pages in your book. I think this has led some authors to try to find ways to get more words on each page to save printing costs.
Tops and Bottoms
The top and bottom margins of your page, depending on whether you use headers or footers or neither, and where you want to put your page info (authors name, page number, and title)
In most books, odd page numbers are on the right and the even page numbers are on the left.
Recommended margins for different book sizes:
5.5” x 8.5”: gutter: 0.75” / outer: 0.625” / top and bottom: 0.825”
6” x 9”: gutter: 0.875” / outer : 0.625”/ bottom: 0.875”/ top: 1”
7” x 10”: gutter: 1” / outer: 0.75” / top: 1 / bottom: 0.875”
8.5 x 11: gutter: 1.25” / outer: 0.875” / top:1.25”/ bottom:0.875”