Make it easy for your readers to navigate trough your book pages, or they will skip your material. Put navigation links on every book page. Do not use too many colors or fancy buttons. There's no need to revolutionize the way publishing is done with your E-book. Check and re-check to see if all the hyperlinks or forms work, and if all the images show up correctly.
Many people forget to link the images or banners to the home directory.
Try to limit the use of images, because they take up a lot of space, and your E-book should not be too large to download. Do this to not distract your readers. Then you have to create an opening page. This page shows up first when your E-book gets clicked on. Be sure to place your E-book title in it, and make an index of all the different pages or chapters.