I am a big fan of books that come in series/trilogies/epic sagas, etc. I especially appreciate when the books are designed well enough that they go together but at the same time get their own distinct look. While looking into well designed book series, I came across a blog entry entitled
The Art of Book Series Cover Design. The first idea that the blog discusses is "the puzzle piece," or a design where all the books in a series fit next to each other to create one design. This is my favorite from the list, though I don't think I've actually seen this in any of the books I've read. Then there's the more common "signature illustration," like in the Little House on the Prairie series below and the Harry Potter series. The blog also talks about "aligned spines" and "title placement," (see Lord of the Rings trilogy below), the "minimal approach" and "striking graphics," the latter of which would describe the Sherlock Holmes series below.
So here is my topic for discussion. What are some examples of really well designed book series, and what in particular connects the books together? On the flip side, what are some examples of more poorly designed book covers in a series and why?