I've read almost all of Michael J. Sullivan's Riyria books (all the prequels and most of the main story - just need to finish the last two books). He's an incredible author and has a knack for creating characters readers can feel something for, plus a story line which keeps one glued to the pages. My favorite aspect of his writing is he usually makes me really think as he explores controversial topics. So, naturally when I found out he was writing another book, one which was completely different than his fantasy novels, I just knew I had to get myself a copy. I dove in with high hopes and Michael delivered. 
 Hollow World is in its own genre. That's part of the beauty of this book. Its not like anything I've ever read before. Its labeled as Sci-Fi thriller, but I don't think that's the best classification for this book. It just didn't feel exactly like Sci-fi to me. Instead, I'd consider this book a hybrid. It has elements of Sci-Fi, but also felt a lot like reading a contemporary novel too. Plus, the entire concept was based on time traveling into the future. The writing was not overly descriptive either, which sci-fi sometimes is. This book begins in current times and then quickly jumps 2000 years into the future to a place called Hollow World, a world underground. Its told in a third person narrative from the perspective of our hero Ellis Rogers. 
 Ellis is definitely a flawed character. He's been married to his wife for over 35 years, but I don't believe he's ever been in love with her. Their only son, Isley, was conceived out of wedlock and the primary reason for their union. He's the sole reason the marriage exits. Its no surprise when he's found hanging from the rafters of the garage, Ellis wife takes off her wedding rings, basically the marriage ends, except for on paper. So, many years later when Ellis finds out he's dying from pulmonary fibrosis, he keeps it hidden from his wife. Ellis is afraid of death. He's only in his fifties and really doesn't want to die. As a last ditch effort to save his life, he decides to attempt making a time traveling machine and travel into the future. Maybe in the future he's find a cure for his ailment. Ellis has the notes from a co-worker who attempted to time travel, but his machine failed because of an error only Ellis reveals. When he builds his own machine, correcting the mistakes, it he's shocked to discover it actually works. Ellis is transported 2000 years into the future to a place called Hollow World and here is where the true story commences. 
 I loved the world building in this book. It was something even simple minded folks could understand. That's rare for a sci-fi thriller. The futuristic inventions like The Maker, a device which could create anything a person's mind could conjure from the past or the Port-a-Com another device for transporting anything from one place to another were all so easy to grasp. This is not usually the case for me when I'm reading Scif-Fi. I do have to mention this is a book I may have to read more than once though to pick up on all the history of how the politics evolved. 
 One of my favorite elements of Hollow World were its people. In this future humans are not longer classified or divided into sexes, groups or cultures. Everyone is the same, created from the same DNA. In this particular future, people actually strive to stand out or be different, a total reverse concept of the conformity which we see of in our day and age. Its wonderful how the Y chromosome was removed and also blamed for all the violence of the world. I got a good chuckle from that! I also adored in this rendition of the future people are actually judged by what is on the inside - not how they look on the outside. 
 Characters in this book were impressionable. I loved Pax right from the start. Even though he was sexless, I almost thought of him as male more than female. He did have plenty of female traits because he was tender, compassionate and a person who wore his emotions on his sleeve. However, he was brave and seemed to hold a position (an arbitrator) which which felt like a man's job. Ellis Rogers, though flawed, appeared to be a good person deep down. He's just someone who made some pretty bad decisions in his life and was suffering dearly for his bad choices. Warren, Ellis's best friend from high school, well, he's someone I didn't trust. He seemed liked he was a very bad influence on Ellis, in both worlds. 
 The way this story wraps up is pretty incredible. The ending really made the story for me. For the entire book, I was craving to know why Isley committed suicide. When it was finally revealed, it was something I never would have guessed. In addition, the way everything comes to a head reminded me of like the way a Western ends with a big gun battle. The last 40 pages or so are just real page turners. This is a wonderful story, one which made me ponder the real meaning of love and to relish the beauty in everything, - especially the rain! 
 I'd recommend this book to anyone who likes to read about concepts which really make you think and re-think your values. Its a story that leaves the reader pondering the direction this world is heading in and wonder where it might end up. For readers looking for something complex, but written in a simple way, this is your book. Sullivan fans won't be disappointed this is another great book. We can only hope he will write many more like it!