Okay, so books were around for a long time beforeHarry Potter. But JK Rowling turned bookconsumption, especially for children, into somethingclose to addiction.
You want proof? The UK release of Harry Potter andthe Prisoner of Azkaban in 1999 was timed at3.45pm to prevent children in England and Walesfrom skipping school to get their copy.
The later books got HUGE but it didn't stop kids devouring them.
Grown-ups got hooked too, with the books being released in adult-friendly covers.
The book releases themselves became headline news: when the fourth book Goblet of Fire cameout in 2000, booksellers around the world got together to coordinate the first ever globalmidnight launch.
When Rowling received an honorary degree at St Andrews University that same year, theScottish institution said she had proved that children's books "are still capable of capturingand enchanting an immense audience, irrespective of the competing attractions of television,Nintendo, Gameboy and Pokemon".
The Harry Potter books are credited with opening the way to a whole swathe load of youngadult fantasy fiction.
Lots of books were released in the hope they would be "the next Harry Potter", such as ArtemisFowl, The Spiderwick Chronicles and A Series of Unfortunate Events.
Would we have had blockbuster series like Twilight and The Hunger Games novels had notPotter paved the way?
And let's not forget fan fiction.
The internet is thrumming with tens of thousands of unofficial spin-off stories about life atHogwarts, The Dursleys and what the Weasley twins get up to at parties.
For a generation of kids brought up on Thomas the Tank Engine and The Polar Express, therewas suddenly a shiny new steam train in the engine shed.
Yes, the Hogwarts Express.
No trip to King's Cross Station in London is complete without a selfie on Platform Nine andThree-Quarters.
Most words have to be around for 10 years before they will be considered for the OxfordEnglish Dictionary, but JK Rowling's word "muggle" - which made its debut in Philosopher'sStone - was an exception.
It was added to the OED in less than half the usual time, appearing in 2002 as "a person wholacks a particular skill or skills, or who is regarded as inferior in some way".
In the world of Harry Potter, a muggle is a person without magical powers.
We suspect that Crumple-Horned Snorkack - an elusive magical creature in Sweden - maytake longer to make it into the muggle lexicon.
In the books, Quidditch is a magical sport played on flying broomsticks, and involves bludgers,quaffles and a golden snitch - a small ball with wings.
In the real world, Quidditch is a non-magical sport played on broomsticks, and involvesbludgers, quaffles and a golden snitch - a person in a yellow t-shirt with a Velcro tail attachedto their shorts.
It started in the US around 2005 and has become a global sport with its own governing body.The Quidditch World Cup takes place annually and was won last year by Australia.
Until recently, the eight Harry Potter films were the largest-grossing film franchise in history,having brought in a whopping $7.7bn worldwide.
The first Harry Potter film - Harry Potter and the Philosopher's Stone - was released inNovember 2001.
As well as breaking box office records faster than a trip on the Knight Bus, it also introducedthe young Daniel Radcliffe, Emma Watson and Rupert Grint to the world.
The final film, Harry Potter and the Deathly Hallows Part 2 (2011) is the highest grossing of allthe Potter films at $1.34bn. It's the eighth-highest grossing film of all time.
The franchise - now known as JK Rowling's Wizarding World - has continued with the spin-offFantastic Beasts and Where to Find Them (2016).
And there's plenty more to come. Rowling has said she has planned scripts for a total of fiveFantastic Beasts films.
Harry Potter and the Cursed Child opened in London in 2016 to the same kind of Pottermaniathat surrounded the release of the books and films.
Some 1,500 fans at the very first performance, many dressed as witches and wizards, gaspedat the various plot revelations and stage illusions.
The two-part play begins with Harry, Ron and Hermione in their mid-30s as their own childrenhead off to Hogwarts school.
The play won a record-breaking nine prizes at this year's Olivier Awards.
Cursed Child will be opening on Broadway in New York in 2018 and JK Rowling has said shewould like it to be seen widely around the world.
Millions of people reaching young adulthood have never known a world without Harry Potter.
Many who've grown up with the books can now get regular doses of JK Rowling via social media- she's got an army of almost 11m followers.
When Donald Trump was compared with Lord Voldemort last year, Rowling tweeted: "Howhorrible. Voldemort was nowhere near as bad."
She later mocked Twitter users who threatened to burn her books.
Twenty years on from that first book, it looks like no-one's going to be saying "Avada Kedavra"to Harry Potter anytime soon.