Michael Vey 3: Battle of the Ampere

The Battle of Ampere is one of the darkest of the Michael Vey books. Hatch takes over the Elgen company by brutally overcoming the board. Characters that we have got to know are killed (as are entire groups of people.) The book starts with Michael Vey hanging out with a native tribe. There he meets another electric child who had escaped from the Elgen compound. They meet up with Jaime who can communicate with the "Voice". They also find the other children are caught. Peru has lost power, and the whole country is against them. This can be both good and bad. (The military are less knowledgable about the "special powers", but they have a lot of military firepower.) Eventually, they escape. Then they have a grand mission to complete to help save the world. However, the bad guy escapes and the book ends with a new mission.
This series now has the feel of a TV show. The main characters go through all sorts of great adventures, but are left essentially where they started, ready to start the next episode, ready to start the next episode. However, we do also have some character development. They go through traumatic experiences, separate and get back together. They feel more unified and are now a team ready to help save the world.