Reply to Comment
ScottEPond said: Wowzer... lot's of great Ideas here.
My two point three five seven cents. People are visually oriented creatures. Yes, they buy books (both dead three and digital) to read the words, but when it comes down to the covers they don't want unnecessary clutter (i.e. extra text that they need to decipher to understand where the story falls into some grander universe.
Being a conveyor of visualosities (yes, I know visualosities is not a real word... I'm working on copyrighting it as I type), I am very drawn to visual representations of stuff like this. I'm leaning more toward Mr_Fahrenheit's suggestion: a visual timeline that you can include in each book to keep things tracked and let your readers see, at a glance, where a particular story or book falls into the universe you are creating.
There is some precedent of using something like a timeline. Robert A. Heinlein (the Grand Master of Speculative Fiction, in case you've lived under a rock your entire life...lol) used something similar and included it in several of his books ("Green Hills of Earth" and "Expanded Universe" I believe). Here's an example of what he did (which I really dig since it almost tells a mini-story in its own right): http://ad7am.tumblr.com/post/950068377/the-heinlein-future-history-timeline-i-owe-more
Visually, it's info-packed, you can see all the currently released stories at a glance, and most importantly it doesn't clutter your covers...
Just my four point eight six seven cents (inflation)...