The 'Harry Potter' series has Harry, Ron and Hermione as best friends. They face numerous challenges together, from battling dark wizards to dealing with school problems. Their friendship is a key element in the story, demonstrating how friends can be like family and stand by each other no matter what.
One great book is 'Anne of Green Gables'. Anne and Diana are best friends. Their relationship is full of loyalty, fun, and they support each other through all kinds of situations. It shows the beauty of a deep and true friendship in a charming, rural setting.
Another is 'Bridge to Terabithia'. Jess and Leslie become best friends. They create an imaginary world together, and Leslie helps Jess come out of his shell. Their friendship is poignant and shows how friends can have a profound impact on each other's lives, even in a short time.