Reasons you buy a book

It doesn't matter if you buy your books online or in a real bookstore. There's always the problem (a good problem ;-)) that there are so many books they offer... We don't have the money to buy or the space to store all this books or even the time to read them all, so we have to choose. And don't forget that we don't want to read all of these books... ;-)

So I thought about the reasons for me to decide if I want to buy a book or not. And here are some of the aspects I consider for my decision...

Things that are important for me to consider buying a book:

• Cover:
  It's the first thing you see of a book. It doesn't matter if you look at it in a local bookstore or online. The first impression counts. A nice cover animates me to pick a book or click on a link to the book and read the synopsis. A cover that looks cheap or ugly in my eyes is a reason for me to not look at the book twice.
• Synopsis:
  I want to know in short what the book is about. I saw so many books that have a bad written synopsis. After reading those you sometimes still don't know what the book is about or even which genre this book is in and that's definitely a reason to not buy a book. Some books try to be intendly secret about the content, but that's a turn-off for me.
  What I also don't like or what I don't look at are quotes from other authors (and newspapers) who recommend a book on the book itself. I wouldn't say that those people aren't thruthful about what they say, but of course authors want to sell their books so they will write those positive comments on the book, but they give absolutely zero information to me as a reader, because they will certainly not write bad things on it. 
• Formats:
  I absolutely don't like hardcover bindings. They are expensive (especially in Germany, because the sellers are not allowed to sell it cheaper), they are heavy and they often don't fit on my shelf.
  I prefer in general paperback versions or because I have a kindle the e-book version. I mostly prefer waiting for the release of the paperback versions to buying the hardcover version. 

So, those are the main factors for my decision. What are your reasons to buy a book? Recommendations? Cover?...