An index can be included within your eBook, but a lot of authors choose not to include the index because eBooks are fully searchable. The reader can use search features on their device to find any word or phrase they would like. Index links are generally listed with page numbers, which can also become confusing when used in an eBook. EBooks do not have actual page numbers (the page references that you see when you read an eBook are generated by the device and they change depending on the font size and type selected by the viewer). When we link an index we link each reference to the content at the beginning of page in the manuscript file. The problem is that what was one page in the original manuscript file can end up being two or three pages in an eBook. So, the reader might still have to turn one or two pages to reach the right content after clicking on an index link.