Scarrow, Alex. Day of the Predator.
Sequel to Time Riders.
Liam and Maddy, Time Riders stationed on September 10 and 11, 2001, are joined by Sal and and a new version of their support unit, Bob, now a woman named Becks. Liam and Becks are sent to stop the assassination of Edward Chan, the father of time travel, but when they are at that period in time, an explosion sends them back to the Cretaceous period... with Chan and several of the students and teachers! The group tries to survive and battles wily dinosaurs while trying to get a message through to 2001 about their coordinates. Meanwhile, in 2001, Maddy is trying to find the group as well as trying to get through to Foster, her mentor, on September 12. The message does get through, but brings with it new risks of time contamination, and the Time Riders have a lot of clean up work to do before they can go back to just monitoring.
Strengths: Dinosaurs bring lots of action to any story, so that was fun. I also liked the secret service agents, even if they were the bad guys.
Weaknesses: Still not entirely sold on the method of time travel presented in this series, but it does address the whole issue of time travel changing the world.
Make sure you check out Charlotte's Library for more books on time travel on many Tuesdays, as well as a fabulous round up on middle grade and young adult science fiction and fantasy reviews.