Source: Review copy from the publisher.
My review of this book is here. After finishing my review, I gave this book to a girl who's turning 13 years old next month. She read the entire novel in one night and told me the next morning, "It was SO AWESOME! I put it down and tried to go to sleep, but I just couldn't until I knew how everything turned out. So I finished it. And what a twist at the very end! When is the next book out?" She recommends it to both boys and girls.
Back Cover Description (highly modified):
What would you do if you could travel through time?
Jax and Isaiah, teen boys from the world’s top science academy, are creating a time machine for their science fair project. Their friends, two girls named JT and Mickey, bet them that their hover-board experiment will beat the boys' doomed-to-fail project in the fair. The race is on to see who will win...
When the boys attempt to go back to 70,000,000 BC to see dinosaurs, the time machine fails though they're sure it should have worked. Then they try to go back 4,500 years so they can witness the pyramids being built as research for an assignment for another class.
Imagine their shock when they come face-to-face with dinosaurs after all! Did the machine glitch and send them back to 70,000,000 BC? No time to test it out--Isaiah needs saving from an angry dinosaur, and Jax will need to convince the girls to help if he's going to save him.