Nomad, by William Alexander (Margaret K. McElderry Books, Sept. 2015), is the continuation of the story begun in Ambassador (here's my review of that one). I hesitate to call it a sequel, because that implies there's a clear cut book one and book two, and Ambassador ended so abruptly, so cliff-hangery, with so much more to come, that it didn't quite seem a complete book on its own. On the other hand, Alexander did an utterly amazing job making Nomad able to stand alone (I know two readers who were surprised there was a first book), while simultaneously picking up what was started in Ambassador and running with it, that I am almost able to forgive him for the trauma of how the first came to a close. But now they are both out, and if you haven't read them yet, get them both at the same time and treat them as one story split into two books, and you will be in for a treat! These books are absolutely top notch sci fi for middle grade readers, and older ones too!
Gabe Fuentes, once an ordinary kid, is Earth's ambassador to a universe full of alien cultures. Every species has an ambassador, and they are all kids, because only kids can use the mind warping mechanism that makes communication possible. Earth doesn't know about Gabe, though, nor do they know that the planet is in danger from an alien race, the Outlast, bent on taking over everything. The Kaen, a nomadic clan of space wanderers, has come to our solar system to escape the Outlast, and Gabe hopes they can help defeat them....but he has not a clue how.
Meanwhile, Gabe's ambassadorial predecessor, a Russian girl named Nadia, has also met up with Kaen. She left her post years back to try a daredevil mission into the travel lanes of another group of aliens...the same travel lanes that the Outlast are using for their intergalactic blitzkrieg. That journey left her blind, with a fried visual cortex (for those who dislike magical/sci fi healing--it doesn't happen for Nadia), and the Kaen have taken her in. Gabe and Nadia, and the young Kaen ambassador, continue to try to find out how they can close the travel lanes....but the Outlast are drawing ever closer, and time is running out.
And Gabe is also worried for his family--his Mexican parents came to the US illegally, and his dad has been deported (and his home blown up, as told in book 1). So the struggle against the Outlast is combined with Gabe's own journey back to Earth to find his father, and sort things out for his family, while being pursued by hostile aliens (as if boarder patrol worries weren't enough).
It is an utterly compelling set up, with utterly compelling characters. That being said, these aren't books I'd give to kids who have to have things Happening all the time; there's rather a lot of fretting in place, as opposed to running around like crazy, acting adventurously. So much fretting, indeed, that I got a bit twitchy from it (possibly I was fretting more than the characters...). But gee, the scope and wonder of the story are mind-candy for readers who are science fictionally inclined. And the themes of communication and seeking safety are timely and well-written without belaboring the point. I also very much enjoyed how much the Kaen appreciated Mayan culture--they met the Mayans when their nomadic path took them past Earth millennia ago, and borrowed many elements of their art and architecture (copying the Mayan pyramids for themselves, in a nice twist on the regular aliens building them stories).
And this time around, Alexander ends with an ending. A good one. (Except I really really want to know what happens to the Outlast ambassador...his story is still a very open ended one and I care about him, even though he was ostensibly the Enemy).
My short answer--it's a bit like David Brin for the young-complicated, very inventive, the believability of its reality stretched almost to breaking point, and memorable as all get out. If you have a young sci fi minded reader who needs a present, do consider these two books.
disclaimer: review copy provided by the publisher for Cybils Award consideration.