Goodreads has completed a survey of their members about how they discovered books. They published the results at the link below.
How do people discover what book to read? Unsurprisingly, word-of-mouth is still king. A recommendation from a trusted friend is the top answer, with "Everyone talking about it" in second place. The third most frequent answer: a book club recommendation. Since book clubs are made up of trusted fellow readers, I would add this answer to the word-of-mouth category. These three answers put together dwarf all of the other responses.
What does this mean for an aspiring author? One thing, and one thing only: write a good book. There are many out there who believe the trick is to jump on the next e-book marketing gimmick. That works ... but only for a brief period. People don't recommend or talk about shoddy books. If word-of-mouth is the #1, #2, and #3 best way to sell books, then authors need to write books that people want to share with friends. As Goodreads says, the survey pointed out "one powerful need:
wanting to be connected with our 'tribe' through stories."
So if you want to be an author instead of a digital huckster, write a good story, polish it to perfection, have it professionally edited and proofread, and then do it all again.