Harry Potter: Book Parallels

If you have not realised it, the books have their parallels.

Book 4

Book 3 – Book 5 / Prisoner of Azkaban – Order of the Phoenix

Book 2 – Book 6 / Chamber of Secrets – Half-Blood Prince

Book 1 – Book 7 / Philosopher's Stone – Deathly Hallows

It would be way too long to write about all the parallels, but take Book 2 and Book 6: 

First, there are the Horcruxes. Harry first destroys one of Voldemort's Horcruxes in Chamber of Secrets and learns more about them in Half-Blood Prince. 

He also learns more about Tom Riddle in both books. 

There are also Tom Riddle's diary and the Half-Blood Prince's potions book. Harry at first trusts them both, then realises that Tom Riddle was his enemy and thinks in HBP that Snape was also his enemy because he killed Dumbledore. 

The mysteries in both books are also plotted out by Malfoys. Lucius in the second, Draco in the sixth. 

Also, Dobby keeps trying to warn Harry in CS about the Malfoys, and in HBP, Harry tells Dobby to spy on Draco for him. 

Harry and Ron take the Polyjuice Potion to turn into Crabbe and Goyle in Book 2, whereas in Book 6, it's Crabbe and Goyle turning into girls.

Nearly-Headless Nick tells Peeves to drop the Vanishing Cabinet in front of Filch's office to get Harry out of trouble in Chamber of Secrets, but Draco mends it and actually uses it in Half-Blood Prince.

Another parallel with the D.A.D.A. teachers: Lockhart seems to be the good guy, which we then later find out to be a fraud, but Snape, though most of us think he's evil, he's actually good. 

Fawkes and Dumbledore have their own parallel. They seem to be very close throughout the series. In CS, Harry sees Fawkes die, signifying Dumbledore's death in HBP. 

In these two books, there's quite a bit that has to do with choice. In Book 2, Harry keeps worrying about the Sorting Hat previously tell him he'd be great in Slytherin, but he only ended up in Gryffindor because he wanted to. Dumbledore says his famous quote: 'It is our choices, Harry, that show what we truly are, far more than our abilities.' In Book 6, Dumbledore reminds Harry that the prophecy between he and Voldemort didn't have to come true, but Voldemort made his own enemy, and also that Harry really didn't have to fight Voldemort, but considering all that the latter had done, Harry realises that, by his own choice, he would fight Voldemort and he would be the one who'd want to finish him off. 

And of course, there had also been the opal necklace, the Hand of Glory, and Borgin and Burkes (see previous post).