Part of Discovery is Getting Your Readers to Share
Let's face it: your book isn't going to go viral if it sits around in people's ereaders and no one ever hears about it. And reviews may be nice, but people read because someone tells them about it.
At the end of your book, right after you 1) told your reader to leave a review, and 2) gave them a link to your site for more information, you then need to tell them to share your book.
The answer came from an unlikely source - a post on an Opera blog by Daniel Davis. He's done all the research to make this happen.
I'm doing some further tests, but this is how they would look in the tail end of the book "J'APE: Just Another Publicity Excuse"
Obviously, there are more steps to be done to make links which will work right inside an epub. But this is on the right track. (Note that each have their own idiosyncrasies, so you're going to spend some time getting this right.) But interestingly, LibreOffice (OpenOffice) doesn't have the problems of having to convert your text over to code - but converts this for you. It's taking some tweaking in Sigil to make it work right, apparently linked images don't port well (haven't tried these before.)
One point to this: use an URL shortener so you can track the "hits" which are coming from your ebook links. And of course, unless you are publishing strictly and forever only on Amazon, they should go to your book's web-page so you can also get a chance for the person to opt-in to your list...
Luck with this - luck to us all.