I posted the cover shot below in a different thread, the "If you purchased this book without a cover..." one. But it is a great illustration of what I personally consider hideous book covers. I like to have a consistent theme for all covers for books in a series. So I can easily tell the group of books are related. For this particular series, the only cover theme I could find that had a cover for all the books was this nauseating one. I'll tell you, it was tough for me to intentionally choose the ugliest covers on Earth just so the books would look like a related group. My mind was so conflicted on that one! And a few of the books in this large series (70+ books) have some pretty neat covers available. But I chose the homely ones for consistency.
Sometimes it is so difficult being a nerd.