In the story, this is what The Saeshell Book of Time looks like. The book glows because it is alive and it controls time. Since no one ever attempted the puzzle about what the cover means, here is one part of it. The infinity exclamation point means infinite possibilities. N! means N factorial, which is the number of possible different arrangements of N things. So infinity ! means the number of ways you could rearrange infinite numbers of things or infinite things happening in time: Infinite possibilities.