Mech Heart & Soul by Ken Deeprose

The people of Cambria are under threat of attack from evil aliens called the Marans. Orin, the genius son of a geeky professor, and his best friend Gigahertz, the most powerful of the planet’s Mechs, will be among those tasked with defending them. Juna, the youngest daughter of the Emperor (but don’t dare call her princess!), worries the Marans are not the only thing the people of Cambria need to fear. Life here simply isn’t fair and she wants to help make things right. Juna hasn’t seen Orin since they were very young, but fate has brought them back together. Now, joined by a diverse group of friends, they must find a way to defeat the Marans, sort the truth from the lies and win back the very heart and soul of the planet.