You could market your plant based vegan E Book by looking for forums that talk about organic food and vegan eating and then if the forum allows place your link to your website in the forum signature and then post useful helpful threads on the Vegan forums.
When someone sees your thread they'll see your link and might click on the link leading to your site and just might purchase your Vegan E Book from you.
You could also advertise your website through google adwords or other ad networks which will help you get more website visitors and hopefully more sales on your Vegan E Book.