Infinity Gate is the first installment of a new science fiction series, Pandominion, written by M. R. Carey. A novel that is not afraid of diving into complicated themes, mostly going around the question of what constitutes conscience, doing an excellent job of worldbuilding, and setting the bases for what aspires to be a big sci-fi saga.

The Pandominion is a federation of multiple civilizations spawning across several multiverses that are alternative versions of the Earth; the access to an infinite number of worlds makes it pretty easy to hop to another world when resources are needed. While the expansion of the Pandominion has been practically unstoppable, the encounter with worlds of sentient machines has recently interrupted it, and it's leading to a conflict against those AIs.
While the Pandominion is pretty open about the acceptance of different species of sentient creatures, this new threat creates a certain paranoia against AIs, despite their society being heavily dependent on it.

The story is divided into three different arcs, which are pretty different themselves, but Carey manages to weave them into an interesting ending, letting many possibilities open for a sequel.
In our first arc, we are going to be following Hadiz, a physicist that discovers the step between multiverses, while trying to investigate the spawn of those multiverses, and the magnitude of the existence of those Earths.
In the second arc, Essien Nnanika is dealing with a difficult life, until he gets to know Hadiz; opening with that access to the multiverse, and leading both to a really traumatic encounter with the Pandominion, which will mark the development of their life from that moment; Essien gets recruited into Pandominion forces.
The third arc is probably the most interesting one, as Paz is a citizen of the Pandominion, so we get inside into how is life there after the encounter with the Ansurrection. Paranoia against the AIs is the main note, with many rights being ignored in the name of order; and we will get to experience how all of this will lead Paz to a really difficult journey that will act as the connector thread between our three characters.

While during a good part of the novel, you, as the reader, are unaware of what's really happening, Carey drives us to an end where all makes sense, and finally, the different perspectives complement between them. Pacing is in a good spot, being slower at the start as we are being introduced to the world, but accelerating as we advance pages, leading to a really frenetic final quarter.

This novel revolves around the question of what can be considered conscience, showing how different creatures/realities have different answers, leading to a conflict because they don't get to understand the other point of view. 
The Step concept, a way of translating between multiverses, but without moving in space remembered me of how the characters travel between Earths in the Long Earth saga, by Terry Pratchett and Stephen Baxter; a nice detail.

The world created for this Pandominion series is literally infinite, with a different version of the Earth in each multiverse, differing in certain evolutive aspects. While all the citizens of the Pandominion are sentient creatures, their evolutive lines are different, as we can observe in the case of Paz.
There are several secrets, like those worlds that were annihilated five hundred years before, that I hope Carey explores more in the sequels, while still dealing with the Pandominion-Ansurrection war.

Infinity Gate is an excellent starter book, perfect for those that like sci-fi that hits you with impossible questions. If you are a fan of the Long Earth saga, I would recommend you try this one. And honestly, I want book 2 as soon as possible.