Great guide, Carl!
I am a very visual person and love tables. Have you thought about adding any tables listing each print and how to get it, etc? I know it is all there in writing, but I was just wondering if you thought about adding it as a sort of "Quick Reference Card."
F.Y.I. I also just discovered that the Observatory and all Space Rockets can be placed on the roofs of your 3 story houses (or any number of stories) to save space. Even though you can't build a fourth floor, you can actually place almost anything up there. It's makes for a great "party area."