Ive published a biography about a guy called Elon Musk (https://leanpub.com/theengineer). I self-published it through leanpub.com. The good thing with leanpub is that their service will automatically generate pdf/epub/mobi files from one main file so you will save time if you need to make a change. The point of leanpub is that you can improve the book as you get feedback from your readers, so my plan is to collect feedback before the big launch at Amazon.

But don't think it's free money - it's still takes a lot of time to write it and it's still difficult to spread the word about the book.