Marco, My Son, My Little Macaroon (Book 15)

Book 15 concludes with a standoff between Vissers 1 and 3, Marco finally revealing the truth about his mom to the rest of the Animorphs, and the question of whether Marco will remain a prisoner of hope. What do you mean this is a book for children?! Why does this book feel like it has the emotional weight of a main series book, but the self-containment of a bubble episode? Rachel is mad at Marco for not killing Visser 1 when he had the chance, but doesn't she miss an opportunity ...