The Experiment is another just OK Animorphs book. It's kind of funny since Ax gets his TV and is very into These Messages, and the reveal at the end is pretty good. However, the rest is just eh. The ghostwriter does a good job writing Ax as an alien though, so that's a plus.
Just one question (an actual question)... not even a very spoilery one.
When Ax is talking about force fields he says the energy expenditure increases exponentially, not 2x but x cubed... that could be correct since x cubed is exponentially larger but would x squared make more sense?