I liked it! The plot flies straight as an arrow with no side-plots that only become relevant 1,000 pages later. I really needed a book like this after some other recent reading!

I 100% agree with Zach's review about the shortcomings. Some basic questions about the Hoops are never explained. For example, each Hoop has two sides. With two Hoops on each world, that's four portals. But the worlds seem to be organized along a string, just one after the other. (Based on the cover and the single points of Sadema and Celema.) So I guess either both sides of a Hoop go to the same world, or both Hoops have one side for each of the next/previous worlds. There are scenes contradicting both possibilities. They definitely travel from Hoop to Hoop, as in Jierra. But they also travel a lot going round and round on the "ring road" around "the hill". They can even walk from world to world, so it sounds like using the same Hoop? (No idea how big the worlds are, but there are cities in them.)

If the ring road just loops around the same Hoop, why do you have to walk the long ring road around it? Why not circle it closer to the edge in two minutes? On the long way to Celema we have this conversation:

"If we stayed at this edge, and just circled it until we hit the nub ... ?" she joked.

"We could try the same measurements," Montano conceded. "And see if the gap was small enough to bridge. But that would be a lot of work, for no reward."

How is that a joke? I was wondering the same thing! And how is that an answer?

Greg Egan's web page with extra explanations doesn't help me on this either. The very first simple example is "if we ignore one of the Hoops and just consider the effects of a single one." It seems to describe pretty much what's in the novel. What does the other Hoop do?

Okay, enough complaining! I liked the characters. They are not very complex, but each of them is an individual and their personalities have interesting chemistry. There are a few evil-for-no-reason characters, but the people we get to know are all really smart and nice. We see a utopistic society in the vein of [b:News from Nowhere|189746|News from Nowhere|William Morris|https://i.gr-assets.com/images/S/compressed.photo.goodreads.com/books/1172550120l/189746.SY75.jpg|13352231]. It also raises a lot of questions that are not answered, but I guess we're here to do topology, not sociology. (I wouldn't have minded.)

The plot has a number of awesome parts that I don't want to spoil. Like suddenly being stranded in an alien land. The ending is indeed abrupt. I kept trying to turn the page. There's not even a "The End" leaf at the end. I don't mind that too much. It's nearly impossible to make an ending satisfying.

PS: I actually figured it all out. It's not well explained in the book, but the worlds are not along a string. They are organized in a cobweb with four neighbors to each world. Hence navigation is pretty challenging. There are many nubs, but Celema is unique. It lies in a "straight line" from Sadema, which they correctly assume would lead them in a loop. Question on Stack Exchange