The special day, first held in 1995, is now celebrated in more than 100nations. Although different countries celebrate it on different dates, Unesco chose April 23 as it is the anniversary of the deaths of two great writers - William Shakespeare and Miguel de Cervantes.
Young Post get into the spirit by choosing the best books for their teammates...
Sputnik Sweetheart (for Mabel)
Mabel adores all things Japanese. If she hasn't discovered them already, any of the books by Haruki Murakami are worth a read.
Of all his novels, Sputnik Sweetheart, which touches on love, loss and everything in between, would make a great start.
I really can't say whether she'll enjoy the ambiguous ending, though. Nonetheless, it'll serve as a great intro to a legendary writer.
The Lost Art of Keeping Secrets (for Joyee)
I often think Joyee belongs to another, sweeter, more innocent era. Her love of Andrew Lloyd Webber, floaty dresses and baking reflect that. This is why it's crucial she reads Eva Rice's The Lost Art of Keeping Secrets, a beautiful, coming-of-age story set in post-war Britain.
Granted, she's not a fan of American rock 'n' roll, so she may not see why such a fuss is made about that genre of music's "invasion". But she'd appreciate the excitement the young characters feel about its birth and increasing popularity.
I feel she'd also love all the talk of scrumptious, cream teas and leafy gardens, crumbling mansions and dinners at the Ritz. Like a grown-up Enid Blyton, it's one of the few stories written in the past decade that can be genuinely described as "charming". A bit like Joyee, really.
The Jin Yong series (for Barry)
The mou hap siu suet (martial arts and chivalry) novels of Jin Yong - the pen name of Louis Cha - make you feel as if you are watching a movie as you read them. That's perfect for a movie addict like Barry. Fear not: there are English translations.
One reminder though: please don't watch any movies or TV series that claim to be based on Jin Yong's novels because they are completely distorted versions of the writer's masterpieces - and really bad.
Norwegian Wood (for Leon)
This is one of my favourite novels written by Japanese author Haruki Murakami.
It tells the story of student Toru Watanabe and his relationships with his best friend, Kizuki, and two women, Naoko and Midori.
It's been made into a brilliant movie of the same name. It is a rather sad story, but I think Leon will appreciate its originality and retro feel - not to mention its quirky presentation, just like him!
Slo-Mo! (for Hei)
Everyone in the Young Post office knows Hei is a huge basketball fan.
Slo Mo!, a spoof autobiography about a talented 2.3m-tall teenage boy rising to fame in America's National Basketball League, will probably manage to keep Hei off work for a few days.
The book, by the American sportswriter Rick Reilly, simulates the engaging struggles an innocent teenage boy faces - exploitative commercials, endless partying, and insane fans - when entering the world of NBA.
The Art of Racing in the Rain (for Susan)
It's obvious Susan and mascot Dennis Goodboy have a special bond; you rarely see one without the other - just like Enzo, the dog, and his owner, Denny, in Garth Stein's book.
What's unique about the story is that it's told from the dog's point of view. I'm sure Sue would enjoy seeing the world through Dennis' eyes. And just like her, Enzo is a firm believer in Mongolian legends.
The Runelords series (for Chris)
We all know Chris always wanted a wardrobe that connects to the magical universe of Narnia.
Given his love for the fantasy genre, he may like The Runelords series by David Farland - a crafty world filled with superhuman warlords, invincible monsters and talking animals (no alpacas, sorry).
In the stories, commoners express their loyalty to their leaders by giving them their sight, wit or beauty through magic, so rulers can better defend them in times of danger. Its clever twist adds a good moral dilemma to magic power. The nine-book series will keep Chris occupied for a good while.
The Truth (for Karly)
Karly probably knew whatever I chose would come back to Terry Pratchett. This particular one, though, she'll find interesting and informative as it explains so many things about newspapers and printing.
It's about one man's compulsion to simply write things down, especially when others don't want him to. To make it worse, he prints the things he writes and he doesn't seem to mind who reads them.
I'm sure she will be nodding along in agreement while also having a laugh.