The sad truth is that most readers don't necessarily buy a book based on reviews. They purchase books recommended by friends and relatives. This is called word of mouth and it is the best form of advertising.
Generating word of mouth is easy if you are a best selling author. New novels by these authors initially sell on name value. Then, if the book is a good read, word of mouth kicks in and does the rest.
Independent authors do not have the luxury of watching their latest book move on to the New York Times bestseller list within a week or two of its publication. Instead we as independents must get the word out on our own through marketing and promotion.
Then, after we have worn out our welcome on the internet and book signings (more on that later), we can sit back and wait for our readers to do the rest. Of course if they don't like the book, then all bets are off and your destiny as a pauper is secure.
If they like what they read and begin to spread the word through texts, the internet, and, oh yes, the spoken word, then maybe, just maybe, for some of us writing will become profitable. Until then it will continue to be, as it always has been, a lot of fun.