In A Wrinkle in Time, what is Camazotz, and why have the children gone there? What is the most unsettling characteristic about life on Camazotz?

Camazotz is
a planet shrouded in darkness or evil, and Meg, Calvin, and Charles Wallace have been sent there
by Mrs. Whatsit, Mrs. Which and Mrs. Who to rescue Meg and Charles Wallace's father, who is
being held prisoner in the capital. Camazotz is particularly unsettling because of its emphasis
on complete, synchronized and unthinking conformity. For example, all the children bounce balls
on the sidewalk at exactly the same time of day in exactly the same rhythm. When one child fails
to conform to the bouncing pattern, Meg, Calvin and Charles Wallace later see him being
retrained to bounce correctly in a cruel way that involves electric shocks. The society,
controlled by an evil entity called It, runs on the premise that complete conformity keeps
everything in order and that order and control lead to happiness, though people are so
brainwashed and controlled that they are devoid of will and hence of any real
joy.