The Collapsium by Wil McCarthy
This is an interesting, and sometimes amusing, romp/comedy of manners around the Solar system in the 26th century. This is a weird world to our eyes - artificial planetes with 1 g and neutronium cores are available to the wealthy, people fax themselves through
matter transmitter (which also renders them functionally immortal) and the wellstone has changed things almost as much with its ability to emulate the properties of other matter, even hypothetical ones.
The book starts with Bruno de Towaji, former consort of the Queen, scholar and inventor, having his morning walk around his own planet. Its an easy thing since the circumfrence is only a few kilometers...
It doesn't linger there, Bruno is summoned by the Queen to assist with a disaster in the making as the ring collapsiter (a ring of neutronium to alter the speed of light around the Sun) as it collapses into the Sun. Bruno is reintroduced into society, solves the problem and then retreats back to the isolation of his little planete in the Kuiper belt and trying to solve some problems.
Then the problem repeats itself, and this time the old solution won't work. And it looks like sabotage. Again, Bruno comes up with a solution and the villain is identified and dealt with. And back Bruno goes...
Then Bruno runs out of neutronium for his experiments. So, he's forced to reestablish contact with the body of humanity. And the moment he does so, he receives a visitor. Himself, with a message... This is only the beginning and leads Bruno back into the Solar system to rescue the Queen, save civilization and make some interesting discoveries.
McCarthy spins an interesting and amusing yarn. Monarchy has made a comeback based on science (humans want monarchy) and its the Tongans since its the oldest extant monarchy at the time. Then there is the society with its minor filips and frills and the importance of style. I liked this a lot, which is odd because it borrows some of Greg Egan's habits of made up physics, but for some reason, it doesn't annoy like it does in
Egan's books. Maybe its because McCarthy banishes the relevant bits to appendices. Another reason is that it has a tight cast of characters, not one of thousands. You do get to know them (typically as Bruno asks questions), and like them even though they can be very silly sometimes.
It's a lot of fun folks. Seek it out and enjoy it.