The Porsche 924 hit the market at a time when Porsche was struggling to make money and stay afloat. It appeared very possible that the company would go bankrupt. The 924 was not only an adequate entry level car, it was a huge hit and one of Porsche's all-time top sellers. It saved the company with a huge new revenue stream. Not only did Porsche stay in business, but they had enough funds to further development on some of their other cars, especially the famed 911 line, which was aging at the time but has since come back with a vengeance to become a very popular flagship car.
The I4 was the only engine for the 924 - first a 2 liter and then later on a 2.5 liter with water cooling. The transmission at times caused problems for drivers. The 5 speed manual sold in 1979 had first gear below the reverse gear on the left hand side. That's unusually, and confused many drivers. That confusion led to many gearbox problems later on. The following year, the shifter pattern was changed to a more standard H pattern used in the Audi.
Although the styling is unusual for the Porsche, it was unique in its time and well-liked by many buyers. The weight distribution also gave the 924 the best handling in stock form for any Porsche, quite a feat for an entry level car.
You can buy the Porsche 924 in classified catalogs like Auto Trader or Hemmings, but I've found that just looking at the listings on eBay is a lot easier and that way you'll always know if the car has been sold or not.