I really liked this one! It had a lot of survival and action, and the plot moved along quickly. Sam's longing for human contact was realistic, and the ensemble cast of teens was fun. The evil scientist working for the aliens was convincing, and there was also a nice question of Sam's real parents and his identity. This seems likely to be a series, and I'm okay with that. I'm curious to see how this continues.
This is a British book, and the British have no compunction about killing characters off. Some are mentioned briefly, but there is at least one death of a major and sympathetic character. We just aren't as used to that in the US, and younger readers might be upset.