Symbolism, Imagery, Allegory
There's heavy overlap between "books" and the Geisel Library. After all, the Geisel Library is ground zero for a fight over whether books should remain old (like Robert wants, at first) or should get new "technology" (as Robert comes to enjoy at the end). While the Geisel Library might fit nicely as a symbol for the fight between old and new in this book, we want to point out that it already was a symbol for that when it was built.
When Robert first comes back to the UCSD campus, he notes that the Geisel Library is "Unchanged after all the years!" and has "nothing virtual about it" (11.42). So it's clearly a symbol for the old way of things?
But Robert remembers when it was built and everyone complained that it was too futuristic:
"We've been hijacked by space cadets." In fact, it did look like something brought down from outer space: the six aboveground stories formed a huge octahedron, touching ground on one vertex and clasped by fifty-foot pillars. (11.49)
We don't know about you, but when we read about a huge octahedron touching the ground on one vertex, we don't think, "Oh, that's so nice and traditional." So even while Robert is thinking that the library is unchanged, we soon get a reminder that the library itself was a huge change to the campus.
In that way, the Geisel Library isn't just a symbol for tradition; it's a symbol for how new things become traditional if they only stay around long enough. Like cars. Or computers. Or the dang wheel.
Geisel is a Living, Changing Library
Which brings us to the final image that Robert has of the outside of the Geisel Library. Robert's first view of the library is marked as traditional: the library is "still" there; it's the oldest building on campus (Epilogue.13-4). After the library riot nearly destroyed parts of the library, the administration didn't rebuild it the way it was (which would be an attempt to recapture the past); and they didn't destroy it and build a new building (which would be a way to throw out the past). Instead, they kept the library the way it was, post-riot, and added some new things on to it (Epilogue.17).
Robert at the beginning of the book would probably scoff at this solution of keeping the old and adding some new bits. But Robert at the end looks at this library that combines old and new and thinks, "this was real. This building lived" (Epilogue.18).
So, we would argue that the Geisel Library is a symbol of mixing old and new—it combines the themes of old age, change, and technology. By the end of the book, Robert accepts that being alive means changing.