So while searching for well designed series, I came across this blog: The Art of Book Cover Designs. This blog gives examples of many great series that were either the original designs or redesigns. Here are the ones I thought were worthy of posting:
Like Katie, I dug a little deeper to find out more about the designer. I was very interested in the redesign of Catch 22 (Rachel, this may be inspiration for your project) which was designed by two people. I came across their Behance page and here are other books they have designed: