Groupon (GRPN 8.21%) is closing out the year with a bang. Shares of the daily deals leader have closed higher in nine of the past ten trading days, eyeing a 140% pop in 2014 with just a handful of trading days left.

It's easy to see why Groupon has done so well this year. The board's move to fire its founding CEO at the end of February was seen as a positive by the market looking for more seasoned leadership, but Groupon has also earned the market's faith. Gross bookings have continued to improve in North America, and the daily deals leader has been consistently profitable on an adjusted basis. 

This isn't the same Groupon that blazed on the scene with its local offers for discounted restaurant, spa, and touristy experiences. They are still there, of course, but Groupon's spike in bookings lately has come largely from the sale of physical merchandise. Margins naturally aren't as plump, but it's still a viable application of its growing base of both customers and merchants.

The number of active customers that have purchased a Groupon over the past year has risen 10% to 43.5 million, and more than half of those are actually outside of North America. 

Groupon customers are a loyal lot, spending an average of $137 on Groupon offerings over the past 12 months.

There's still room for improvement, particularly outside of the growing U.S. market. Gross billings surged 20% in North America in its latest quarter, but it suffered a double-digit percentage decline everywhere else.

Groupon has made the most of its growing list of contacts to push other merchant services including credit card processing.

The flash sale darling is in a good place. It's been buying back stock, and it has more than $1.1 billion in the bank for more repurchases or to continue its role as a serial acquirer. Wall Street also sees net margins widening in the coming year. Analysts see Groupon earning just $0.09 a share this year, but that's expected to expand to $0.25 a share next year.

Despite this year's spectacular gains, Groupon continues to trade well below its 2011 IPO price of $20 a share. That just goes to show what a wild trading history the stock has achieved in its 25 months as a public company.

Groupon was one of last year's biggest losers. Now it's one of this year's biggest winners.