This is between 4.5-5 stars, so I'm rounding up. 
 Right now this is one of my favorite YA books read this year, as well as my favorite YA Sci Fi book read in recent memory. 
 I fully do realize that a part of my excitement for this book is that it is a YA book with NO ROMANCE. I can't remember the last time I read a YA book that didn't have romance. Middle School books, yes, but not YA. 
 It's not that I hate romance, but it was sooooo refreshing to read a book that in the middle of a battle with a semi-sentient AI bent on destroying everyone, there wasn't a subplot about unrequited love, or which of 2 suitors to pick. And it could have happened, and might have even worked for me, but the story worked so well without it that I'm glad it wasn't added because "that's what you do these days with YA." 
 I get asked by folks to recommend books, and a common question I get is if I know of any new YA titles that don't have romance. Now I have an answer. 
 Katya's World is action-adventure set on a planet completely filled with water, so everyone travels by submarine. I freaking love anything with submarines. I used to watch the Disney version of 20K Leagues over and over again. I wanted to live on the Nautilus. My inner child is still squeeing. 
 Katya's ancestors were colonists from Earth who braved a new, harsh environment and survived. When the Earth, or Terran, forces finally came to "check on them", the colonists weren't interested in being ruled by anyone other than themselves. Cue a war that the planet is still recovering from. 
 Katya has finally earned her license and is ready to start working on her uncle's sub. Kids grow up fast here, and they have an ingrained sense of responsibility and rugged determination. Without it, they wouldn't live very long. 
 Her uncle's sub is commandeered by a Fed transporting a prisoner. Soon, they make contact with something that the Terran forces left behind and Katya is on an adventure that will test her trust in others, her bravery, and her skills. 
 Katya was strong, older than her years, very smart - my kind of lead. Kane is an intriguing character. I got in the end why he did what he did, but sometimes I had to wonder. I thought the other characters were well done as well. This is the first book, so there is a lot of introduction. It will be interesting to see where it all goes next. 
 There is a lot of action here, and I felt like I was hurtling to the end, but it kept my attention and I really enjoyed the book. 
 I will be eagerly awaiting book 2. 
 [Received an ARC to review.]