I'm a librarian who loves anime, manga, and reading a wide variety of genres.
This list is inspired by a recent freebie-browsing session on Smashwords.
1. Awful cover art. Yes, I judge books by their covers, especially when I'm trying to quickly browse a few hundred of them. Pretty cover art doesn't necessarily mean the book is good, but it at least makes a good first impression.
2. Grammar/spelling/punctuation/word choice mistakes in the blurb (or the title *sob*). It does not bode well for the book itself.
3. It's in the "New Adult" category. I have a knee-jerk "no" reaction to these.
4. Blurbs that don't make it clear what the book is about. Especially when the blurb is written in the first or second person.
5. Blurbs that are just random combinations of letters. I can't believe I have to add this to my list, but I just spotted one of these today. I can only assume that the person who uploaded the e-book had no idea what they were doing.
6. Blurbs that start with comparisons to big-name authors or with quoted praise. I don't mind this kind of thing as much when it's done with traditionally published books, but the authors usually aren't the ones writing the blurbs in those instances.
7. Any indication that the work has not actually been completed yet. I'm not downloading an incomplete book.
8. Blurbs that start with "What would you do if __?" "What would you do if zombies took over? Find out what John Doe does in this book!"
9. Excessive exclamation points.
And all of this is before I even get to the excerpts.