David Massie and the Hidden Underworld is the second book in the David Massie series, unfortunately I haven't read the first book David Massie and the Quantum Flux. From what I gathered from the synopsis on Goodreads, David and CP; a Time Cop were successful is solving the mystery of the Quantum Flux. Now having returned from their mission, David is back at school when everyone in his history class, except him and Rory are frozen in time. CP tells David that the Time Police Depot was destroyed along with all the other Time Cop's. It seems a Dark Armored Warrior is now on the loose. In order to save the planet, David, his crush Rory, and CP must travel back in time to ancient Greece and locate Pax, a scientist who can build them a reality gate before the Dark Warrior can destroy their world.

The Hidden Underworld is an interesting science fiction with some fun tech heavy components. There's CP the last remaining Time Police officer, who is tasked with keeping the timeline intact. There are robots, Greek gods, interstellar time travel via a spaceship that's more like a SUV but can cloak itself to blend in as a chariot, there are battles with blasters, and even reality gates. There is also the added mystery of what happened to David's older brother, Morgan who vanished in the first book of the series. Some of the highlights of the book are the light flirting that goes on between David and Rory and the teasing from CP. I also really enjoyed the parts when they end up in ancient Greece, although I do wish the author would've expanded on this a bit more. Overall, the story is on the shorter side, which on the one hand would be good if you're introducing a reader to science fiction, but for me, I would've enjoyed more. It felt like just as the action was building, things ended and will most likely be continued on into the next book. At the same time, I think this will certainly have kid appeal for its time travel, action and who wouldn't enjoy learning about CP the Time Cop? ** A huge thank you to Books Forward for the recommendation and NetGalley for the E-ARC **

What worked:
The book presents an intriguing tale of time travel. Time Police have the responsibility of monitoring events and stepping in when disruptions occur. All of them were killed in the previous book except for CP and David, and CP is now determined to exact revenge against the Dark Armored Figure. The jaunts through time are almost instantaneous, as CP, David, and his girlfriend Rory try to repair a destroyed reality gate. The author saves some surprises about an important character that will alter the future of the series.
The banter between characters is amusing. CP likes to tease David and Rory about their relationship which usually results in much blushing. The couple finds time to act like kids and to share their feelings with each other. David likes to make snide comments and call CP “Ace” when things don’t seem to work out as planned. CP usually gets the final word when his ideas actually work to save them. These interactions typically happen during action scenes when situations look dire.
The story includes a blend of elements from various supernatural genres. A spaceship SUV is able to transport the characters through time and then move invisibly around ancient Greece. Robots help with cleaning and flying the ship, although the antagonist modifies them to attack and defend. CP and David wield blasters, and David has a watch that allows him to create useful holograms. These things contrast with common Athenians found thousands of years ago, although one citizen isn’t fazed by the concept of time travel.
What didn’t work as well:
This book is very short at less than 100 pages, so it doesn’t include a great deal of description or detail. Rather than describe well-thought-out plans, the characters often resolve issues by pushing a button to capture attackers, escape a formidable situation, or create items from nothing. I prefer when characters use their wits and materials on hand to take care of their problems.
The Final Verdict:
This book has creative technology and the potential problem of an evil character gaining access to traveling anywhere in time. A longer version of the book would allow the author more time to fully develop the characters, the conflict, and the overall story. The book is still entertaining, and lovers of time travel should definitely check it out.