Launched a few weeks ago, The Queen's Birthday Book, a digital log created by British entrepreneur Jonathan Haward, has already garnered birthday greetings from around the world, including Australia, El Salvador and Fiji.
A 12-year-old girl named Isabella wrote a long, chatty note that said, among other things, "I hope you get to read this because now you know that there is a (nearly) teenager in London that is hoping to become a politician one day, rather than a pop star." Isabella advised the monarch that birthdays are nature's way of saying, "eat more cake."
A man from India wrote, "Best wishes from the largest democracy to the Queen of one of the last few kingdoms in this world."
Others have remarked on the Queen's love of horses, her perseverance through difficult times and her lifelong devotion to country.
"It's been lovely so far," Haward tells PEOPLE.
The book is the outgrowth of a devastating personal loss.
In 1988, Haward's brother, Royal Air Force Group Captain David Haward, was killed while piloting his Harrier jet.
"Losing him left a big hole there for us all," Haward says.
When a friend sent Haward a picture of his brother climbing into the Harrier for what would be his last flight, he used that and other photos to set up a commemorative web page. Word of the page spread, and soon Haward was creating similar pages for others, where people could leave comments and also donate to the loved one's favorite charity.
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"I was amazed by the messages of condolence and comfort," Haward says.
Then along came Queen Elizabeth's Diamond Jubilee in 2012, when Haward asked well-wishers to pledge 60 minutes of their time doing something "legal, decent, and honest" in honor of the 60-year reign. The Queen "saw the book and was delighted," Haward says.
The new birthday book will be kept open for the rest of the year, and eventually will be presented to the monarch on a dedicated iPad.
"It will be an enduring gift to her," Jonathan says, adding that it will remain online as "an important part of social history."