Following on from last year's "fleet of worlds" this book continues the story of known space, primarily from the viewpoint of the puppeteers and Niven's 2nd best characterised ARM agent, Sigmund Ausfaller, who as an extremely talented hyper paranoid hunts down and blocks perceived and real threats to Earth. This narrative again mixes several threads, Ausfaller's partial unravelling of the puppeteer conspiracies on Earth and elsewhere, Beowulf Schaeffer's entanglement with Ausfaller and his attempts to get free and the various political machinations of characters from earlier works and the puppeteers themselves, especially Nessus. It's a fast paced book and highly readable with a satisfying structure which builds to a series of revelations about events described in other known space books.
But if you are new to Niven's known space works, don't start here.
Basically Larry Niven is using this latest set of novels to tie up every element of his previously published known space works into a single cohesive narrative, where all characters, events, "use one time" plot devices, simple mistakes, throw away concepts, pretty turns of phrase etc are tied up and wrapped behind the over arching puppeteer conspiracies and the very human-centric events of the earlier works are illuminated by the larger scale, longer time frame point of view of the puppeteer homeworlds.
Now I'll take any new writings about known space with little complaint and I'll devour them in a single session. I've been reading Larry Niven stories since I was 7 and I've always loved the known space stories for their cohesive narrative/history without Larry being too being forced to concede too much detail to the reader, letting my imagination run riot with known space and "fill in the gaps myself" so to speak.
For that reason I have trouble with this exercise in over-explaining or rationalising known space. Niven flagged this idea in some of his anthologies as a way of "destroying" known space as an ongoing narrative playground by exposing all the human and other events he'd described as being driven by an alien conspiracy.
Frankly, Niven was right to ditch this idea back in the 70s, reviving it now and changing the conspirators to the Puppeteers doesn't make it any better and unless Niven is using this as the basis of a very complex role playing computer game (which BTW I'd buy in a flat second) I'd give this up as a bad idea.
And finally, a direct appeal to Larry Niven himself, what have you done to the outsiders? Without spoiling anything for other readers this is a pointless and terrible plot device with limited payback for either the reader or your new view of known space. It's just removal of yet more magic from the whole narrative playground, utter madness.