The friendship between Harry, Ron, and Hermione provides an emotional core to balance out what would otherwise be a really fast-paced and intense series of novels (after all, wars against evil do not make light reading). In Chamber of Secrets, these friendships are what keep Harry going as the rest of Hogwarts begins to suspect him of being the Heir of Slytherin. It's only in the later books (e.g., Ron's feud with Harry in Book 4 and Hermione's annoyance with Harry's bad temper in Book 5) that J.K. Rowling starts exploring the pressures in Harry's life that arise when his friendships aren't there to support him.
Questions About Friendship
We get to see a little bit of Draco's interactions with Crabbe and Goyle when Harry and Ron take Polyjuice Potion. Like Harry, Draco has two primary friends. But how does Draco treat his friends? What is his definition of friendship? What does his behavior towards Crabbe and Goyle indicate about his character?
How does it make a difference to Harry, Ron, and Hermione's friendship in Book 2 that Harry and Ron are boys and Hermione is a girl?
How does Voldemort use Harry's strong sense of personal loyalty and friendship against Harry? Is there any way for Harry to protect himself against such manipulations?