I have finished reading Rainbow Mars by Larry Niven.

It is the year 1108 AE (Atomic Era, starting in 1945 with the first atomic explosion). In this post industrial age almost all plant and animal life has been driven to extinction by the poisons of industry in the air and water, leaving only the humans who were able to adapt to the pollution, and the farmed yeast they live on.  Waldemar the Eleventh  is the new Secretary-General, the latest in the line of monarchy of leaders of the United Nations. Waldemar the Tenth liked extinct animals, Waldemar the Eleventh likes planets and the stars, and they say he is not a mental deficient (unlike Waldemar the Tenth who was 26, but whose inbred family had left him with the intelligence of a 6 year old). Hanille Svetz, an agent for the Institute of Temporal Research, no longer being sent into the past to find extinct animals, is now assigned to travel to Mars’ past, when canals were observed on the planets surface, and find Martian life. They find much more life than they expected, including a giant tree extending from the planet’s surface into space. As usual, the mission does not end up going the way it was planned. They end up in earth’s own past struggling to make it back to the present, and then to restore the time line they knew.

This book was a little hard for me to get in to at first, as the writing style is so drastically different than the Heinlein and Varley I have been reading recently. It seemed somewhat less smooth, and the temporal jumps and paradoxes left me struggling to follow it at times, but the overall premise was interesting enough to keep me going. They use ‘extension cages’ to travel in time. The cage itself is just the vehicle attached to the time machine which stays in the present time. The arm between the two “fades off in a direction the human eye can’t follow”.  Time travel is still somewhat difficult and very expensive and is reserved for satisfying the whims of the current leader. Post industrial humans have evolved to breath the polluted atmosphere, and now cannot breathe pre-industrial air as it does not have enough carbon dioxide in it to trigger their body’s autonomic breathing mechanism and they just forget to breathe. They use a filter hood over their head which passes the needed gases in the needed ratios for them to breath in the past, or in a martian atmosphere.

After the main story ends, this books includes several stand alone chapters covering the earlier exploits of Svetz, which were eluded to in the main story line. With tidbits of incomplete information from ancient children’s books, he goes to recover extinct animals from the past, often ending up with something which was not exactly what he went looking for. These actually helped fill in a lot details for me and in some ways I enjoyed them as much if not more than the rest of the book, or at least they increased my enjoyment of the main story. I am not sure, but I almost think these should have come first.
Even though I was not so sure in the beginning, by the end I ended up enjoying this book quite a bit, although I am not going to run out and find more books by Larry Niven to read. I think he might be best known for his Ringworld series.