(Re-read this as part of summer-long nostalgia trip of Larry Niven's Known Space books. Although [b:A World Out of Time|64725|A World Out of Time (The State, #1)|Larry Niven|http://d202m5krfqbpi5.cloudfront.net/books/1348613073s/64725.jpg|1634535], takes place in a different fictional universe, I had good memories of the book and this felt like the right time to revisit.)
There is one major difference between this book and any of the Known Space series that you should know about --- no FTL --- hence no hyperspace, no Outsider drive, no instantaneous communication. What we have is the lightspeed-observing Buzzard ramjet - on a trip to the core of the galaxy. With this key limitation, Niven's narrative has to work with centuries of transit time, long stretches crossing the empty gulfs of space, and all the arcane physics dealing with astrogation, cosmology and time dilation. Is the master up to the challenge?
In [b:A World Out of Time|64725|A World Out of Time (The State, #1)|Larry Niven|http://d202m5krfqbpi5.cloudfront.net/books/1348613073s/64725.jpg|1634535], the protagonist, Jerome Corbell, travels to the core of the galaxy and back, over an external elapsed time of 3 million years and Corbell's body clock of about a century and a half. He returns to a solar system that is drastically changed, with the sun cooler and red, and Earth in orbit around a warmed-up Jupiter. Then the action shifts groundside as Corbell explores the plate-shifted continents. Niven sprinkles this with antagonists/allies, including the digital entity, Peerssa, the aging dowager, Mirelly, and a troop of the human post-genitors, the immortal Boys.
The narrative is sequential; each change in time and setting is essentially a stand-alone story. The first half of the book is fast-paced and unpredictable; all about the physics, with vintage hard SF story-telling from Niven. The second half, taking place on Earth, is more tourist-y with some emotional impetus from Corbell-chasers. Though the tale still moves fast, it is oddly thin without the heavy science. It can only end one way, and does.
The expected Niven themes are here: immortality, highly intelligent, rational characters, logical development and framework, sexual motives. If I stopped halfway, this would have been 5 stars, but the balance of the book really didn't work as well and so my updated rating. I think Niven used what he learned from this book to write better books later in his career. He also learned to avoid the slower-than-light backstory and embrace hyperspace. He must have liked FTL so much because he later made up Hyperspace II.
Post-script: Notwithstanding the challenges, writers still try galactic space opera without FTL. One such is [a:Alastair Reynolds|51204|Alastair Reynolds|http://d202m5krfqbpi5.cloudfront.net/authors/1369753656p2/51204.jpg] with his [b:Revelation Space|89187|Revelation Space|Alastair Reynolds|http://d202m5krfqbpi5.cloudfront.net/books/1306807253s/89187.jpg|219037] series and the recent [b:House of Suns|1126719|House of Suns|Alastair Reynolds|http://d202m5krfqbpi5.cloudfront.net/books/1328058140s/1126719.jpg|2020929]. It does require a real nerdy writer though.