<i>Echo of Worlds</i>, sequel to <i>Infinity Gate</i>, picks up where <i>Infinity Gate</i> left off, without interruption or major change of perspective. <i>Infinity Gate</i> focused mostly on the individual stories and backgrounds of the protagonists (Hadiz Tambuwal, Essien Nkanika, Moon Sostenti, Topaz Tourmaline Fivehills a.k.a. Paz, Dulcimer Coronal a.k.a. Dulcie, and Rupshe), and only nearing the end, all story lines converged. With all main characters together in the same place now, the second book evolves completely around the war between the Pandominion and the Machine Hegemony.

Rupshe devises a plan to end the war, and the team members part ways at times to go on smaller team missions that help this plan. This means there is a lot of variety in multiple adventures. Action scenes and calmer scenes alternate. In order to make the story even more appealing, a new powerful entity is added alongside the Pandominion and the Machine Hegemony: the Mother Mass. It all combines into a heck of a story with a rather unexpected conclusion (and an unexpected narrator we finally get to know).

One outstanding strength of the book that I particularly want to mention is the chemistry between several of the characters, and mainly when Moon or Paz are involved. Both beings –called selves because they are sentient, unlike AIs– evolved from animals like humans did, but Moon is of feline descent and Paz is of rabbit descent. You could easily forget they are not human, but the author created them well and retained certain characteristics of their animal ancestors, which leads to great and/or funny dialogue at times.

<blockquote><i>
She paused, giving Paz a quizzical appraisal. “Also, bunny in heavy armour. That’s both cute and hilarious.”
-- Moon, after Paz put on an armour suite
</i></blockquote>

I found <i>Infinity Gate</i> fantastic. I believe I like <i>Echo of Worlds</i> even better. While reading it, I realised more than once that the entire story must have been planned meticulously beforehand. It was so nice to discover that seemingly random facts that I assumed where only added to spice up the characters’ backgrounds in the first book, now came back as important. Nothing seemed left unused. However, not everything is brand new. Some of the ideas were already used in the past by other authors. Fortunately, it never feels “borrowed” because <b>Carey</b> adds a lot of his own, which makes the end result very fulfilling and definitely a recommendable read.

This was an absolute blast from start to finish. Building on the very strong foundation of its predecessor 'Echo of Worlds' hits the ground running on its way to delivering a complex and satisfying ending. It's satisfying to be given a complete sci-fi story of this nature over a mere two books where the norm may be to stretch out the story further, though I would very happily return to these characters and parallel worlds.

If I had one complaint, it's that the climax relies too heavily on convenient coincidences. That aside, I heartily recommend this to anyone who enjoys a well-constructed and original sci-fi story and wants to feel the force of a roller coaster in paper form.