The idea for celebrating such a day comes from the Spanish province of Catalunia - the bookshops gave a red rose for each book bought that day, April 23rd.
April 23, 1616, was also the day two great writers died - Miguel de Cervantes and William Shakespeare (ironically, assumed to be born on the very same day, April 23, 1564). That is also the day of birth of other eminent writers: Maurice Druon (born April 23, 1918) and Vladimir Nabokov (born April 23, 1899).