What Makes You Buy a Book?

This is something I've been thinking about quite a bit, lately. Not really about my own book coming out in a year (though I imagine I'll start thinking about it more in due time) but because of Twitter.

I have folks follow me, then when I go to check out their tweets it's nothing but an endless line of blurbs about their book. Retweets about their book. More blurbs about their book. Everything is endless self-promotion.

This DOES NOT make me want to buy a book.

However, if a Tweeter is friendly,...