In an era of “Me-me-me” millennial hook-up culture, one dating Web site has taken the Internet by storm – 40 Days of Dating is an experiment in dating. And in commitment.

The premise is simple: Tim and Jessie have always had “opposite dating problems” —  she falls in love too quickly, he’s afraid of commitment.

Their solution? In March, long-time friends Timothy Goodman and Jessica Walsh decided to try an experiment.  They would date each other for forty days.

“It takes forty days to break a bad habit,” Walsh explained to CNN.

They set a few ground rules: they weren’t allowed to see anyone else, had to go on regular dates, see each other daily, and attend couples therapy.  Over the course of the 40 days, they both also filled out daily questionnaires, which have been at the heart of their beautifully designed Web site.

Since July, they have published a post a day in chronological order. Today, they published day 40.

The daily blog posts developed such a large online audience that Walsh and Goodman are considering cashing in on the hype and their following. In an interview with Nia Malika-Henderson on PostTV today, they said they will definitely be turning the experiment into a book and are evaluating next steps when it comes to possible movie deals.

But part of the magic of the atypical experiment has undoubtedly come from being able to watch their relationship unfold in real time.

The first few days are awkward and tense.  She gets headaches.  He gets grumpy. Their friends aren’t so sure it’s a real relationship, or even a good idea.

On one of their first dates, she notices, “He is not very good at sharing. As we were paying for the bread pudding, he decided he wanted it all to himself, and told me I should get my own!”

Then slowly, they start falling for each other. The site begins to read like the diaries of a real couple: They cook dinner together (his favorite moment), go to parties and even spend a day holding hands (her favorite moment).

Day 33: Hand-holding from 40 Days of Dating on Vimeo.

But what happens on day 41? Can they really change?  Will she be able to slow down, will he able to commit?

On day 31, he wonders, “Am I really a coward? Perhaps. As I’ve said, something is holding me back. And it’s not just about having commitment issues.”

So do they end up with a happily ever after? We’ll tell you one thing: They both agree Day 39 was the worst moment of the experiment.