I like a nice cover on the book, but I'll buy a book based on the blurb. I will also admit that covers catch my eye.
Here are a couple of STUNNING covers for two Ian MacDonald books:
Desolation Road
Ares Express
Desolation road is one of my favourite books, and my old copy was falling apart. I bought the re-release and was HORRIBLY disappointed in the number of errors in the book. It was like someone scanned it with a document reader and didn't bother to check for errors. I wish I had left it on the shelf.
Ares Express I started reading but couldn't get into it.
I guess it's content after all