What Influences a Reader to Buy a Book?

My next release, OUT OF THE FRYING PAN, comes out on September 6th, so currently I'm hot and heavy into panic mode. Happens every time. The pre-release panic causes night sweats and eating excessive amounts of chocolate as I struggle with the same question yet again . . .

What influences a reader to buy a book?

If I can answer that question, then shazam! Instantaneous sales and gobs of fame, right? Uh...yeah...not so much. Because as I've found out by researching this question, a lot of what influences a purchase is out of an author's control.

THE TOP INFLUENCE
Turns out that readers really do judge books by their covers. That's the number one influence. Dang it, because authors have little to no say in what goes on the cover.

But lest I sink this boat into an ocean of depression, it also turns out there are other reasons potential readers snatch up a book, and here they are:

• Book reviews
• Genre
• Who the author is
• Blurb on the cover 
• The first page
• A friend's recommendation

So obviously I'm stressing over nothing, because most of the things on that list is--again--out of the author's control. Not that marketing isn't important, it's just not something to get all bent out of shape about.

What influences you to buy a book?