The book's title comes from Shakespeare's play The Tempest:
How many goodly creatures are there here!
How beauteous mankind is! O brave new world,
That has such people in't!
Act V, Scene 1
Miranda has been exiled on an island from an early age with her father Prospero. She makes this remark when she sees other human beings for the first time. But these same people plot against her and her father. Miranda is so overcome by the wonder of encountering other humans that she can only see good in what is actually wrong or dangerous.
The character of John in Brave New World is similar to Miranda. He is overwhelmed by the beauty of the people from the new world, initially blinding him to their flaws.
Follow this link to shmoop.com for a character study of John and a look at the importance of Shakespeare in Brave New World.