Obviously you pick up on many new plot points and details (Slytherin’s locket was first seen in Order of the Phoenix! Sirius is first mentioned in Philosopher’s Stone!) but the eyes of someone in their twenties also pick up on a lot of things we, as children, were simply too young to see.

Ron was AWFUL at wooing Hermione

How frustrating was it that Ron and Hermione didn’t kiss until the Battle of Hogwarts in their final year? Sure, little things like Lord Voldemort certainly got in the way, but for the most part, let’s all just agree it was Ron’s fault.

During the Yule Ball in Goblet of Fire, Ron had his first shot at asking Hermione on a date, but blew it by saying: ‘We need partners, we’re going to look really stupid if we haven’t got any,’ as his excuse for asking her. He then spent the entire evening unreasonably stewing when she bagged Triwizard champion Viktor Krum as her date. But it didn’t end there; when Hermione asked Ron to the Slug Club Christmas party, he somehow messed that up too, by going out with Lavender Brown – which obviously saddened Hermione further.

And that’s without mentioning all the sarcastic comments, making fun of the things Hermione cared about (like S.P.E.W.) and just generally being immature. No wonder Ron ended up reading a book called Twelve Fail-Safe Ways to Charm Witches.

And Harry wasn’t exactly great with the ladies either

Look, we understand that Harry had a terrible time of it, but there were numerous times when his adolescent behaviour was pretty unreasonable – especially in Order of the Phoenix. When he wasn’t yelling at his friends, he was upsetting his new girlfriend Cho Chang – whose previous boyfriend was Triwizard champion Cedric Diggory.

As if being a teenage boy with your first girlfriend wasn’t hard enough, Cho regularly and understandably burst into tears about the death of Cedric. But Harry’s awkward approach – trying to change the subject – just upset Cho further. Not to mention the fact that he accidentally invited Hermione on his Hogsmeade date with Cho. Come on, Harry!

The house-elf situation was so much worse than we initially realised

As children, the house-elves often seemed adorable, quirky and helpful. As grown-ups, however, the full scope of just how traumatising their lives must have been fully comes into effect.

Creatures confined to being servants, who get incredibly upset if they are put in a position where they must disobey their masters? Hermione, always far older than her years, was heavily mocked for her organisation S.P.E.W. – but now we appreciate her wisdom.

Wizards were more advanced than Muggles by centuries, but why did they still use quills and parchment?

Surely biros are easier. Or how about electricity? Or the internet?

Viktor Krum was a bit forward

During Goblet of Fire, suave Quidditch star and Triwizard champion Viktor Krum only had eyes for Hermione. This is all lovely and everything, but during the Tournament’s second task, Hermione is taken as Krum’s person that ‘he’ll sorely miss’ and plunged into the Hogwarts lake for him to save.

Alongside that, Fleur’s sister was taken, Ron – Harry’s best friend for four years – was taken, as was Cedric’s girlfriend, Cho. These all make sense. As for Hermione and Krum? They’d known each other five minutes. It’s like saying ‘I love you’ on a first date.

Befriending Harry must have been so hard for Dumbledore

When we were first introduced to the wise and warm-hearted Professor Dumbledore it was almost impossible to believe that his life could be anything more than happy memories of sherbet lemons.

Of course, as time went by, we realised just how much Dumbledore really held on his shoulders – such as the prophecy of Harry’s fate, along with the tragic memories of his own childhood past. Imagine trying to avoid the question of a young, 11-year-old Harry, who had just come face to face with Voldemort for the first proper time, on why this horrible wizard seemed to hate him so much? Imagine telling Harry he saw a pair of socks in the Mirror of Erised, when in fact he saw his family, whole and alive again.

Hogwarts students don’t have to study maths

As if it wasn’t enough that wizards attended a school that could teach them how to turn things into other things, how to fly or how to fight Dark magic, there was one other key bonus point about going to Hogwarts School of Witchcraft and Wizardry: no maths. Do you hear? There was no maths – possibly the worst subject in Muggle education history.

Okay, so there was ‘Arithmancy’, which Hermione studied alongside every other subject under the sun, and it sounded pretty close. This focused on the magical properties of numbers rather than, say, simultaneous equations, but even that sounds enjoyable. Life isn’t fair.

The Dementors are an allegory for depression

As children, the Dementors were fearsome, cloaked and terrifying to any young reader. As an adult, their presence is even more horrifying when you realise they symbolise depression, as J.K. Rowling has confirmed before in interviews.

Then the descriptions suddenly feel all the more powerful, especially during Prisoner of Azkaban, where Harry fears he is ‘weak’ because he suffers at the hands of the Dementors worse than others.

He hesitated, and then the question he had to ask burst from him before he could stop himself.
‘Why? Why do they affect me like that? Am I just –?’
‘It has nothing to do with weakness,’ said Professor Lupin sharply, as though he had read Harry’s mind. ‘The Dementors affect you worse than the others because there are horrors in your past that the others don’t have.’
Harry Potter and the Prisoner of Azkaban

The books teach us a great deal about prejudice

The awful attitudes towards Muggles from certain Dark wizards is horrible to read as a child, but growing up among the real-world issues of prejudice, we truly understand how dark the world can be, Voldemort or no Voldemort.

In J.K. Rowling’s treatment of the divide between the magical and the non-magical, pure-bloods and Muggle-borns, we realise that she was teaching a very valuable lesson about society – and creating a generation very knowledgeable about kindness and tolerance.