It's just like Monopoly, only it does EVERYTHING better.
Drawing parallels between this game and Monopoly is pretty much inevitable. I usually disregard any other game when reviewing, but I'm making an exception. But the amount of things that it does better than Monopoly is mind-boggling.
Anyone who has played Monopoly according to the official rules once or twice can probably agree that it can devolve into roll dice/pay money/repeat for way too long without the board changing much at some point. Fortune/Boom Street can have that problem, but it's much rarer. The game's pacing is many leagues better than Monopoly.
Playing by Standard Rules, stocks introduce many new elements to the game, including, among other things, dividends (when one lands on another's property, the district's stockholders receive a little extra cash), which does a lot to help the game's pacing by introducing more money. Each dividend is small, but they add up.
The objective is not to bankrupt other players (though it's an alternate win condition), but to gain enough money and assets to reach a target amount. The amount can be adjusted to some degree if you're not playing in the single-player tour mode, so you can make a game as long or short as you want.
You can invest money into any shop you own regardless of whether you own other shops in the district. Owning other shops in the district increases the amount you can invest, as well as providing an additional multiplier to the price others pay when they land on it.
But the main thing that this game does to help the pacing and overall variety of the game is forced buyouts. If you land on a property someone else owns, you can pay 5 times its value (after paying the normal price for landing on it, of course) and take the shop without its owner's consent. I've not played all that much Monopoly, but I do remember my opponent never parting with the shop I needed to complete a monopoly of a district and allowing me to actually get closer to victory. While it's possible for a forced buyout to allow a game to drag on a little more (by buying a shop in someone else's monopoly), the act of changing the board in such a way is enough to keep the game fresh and entertaining for as long as it needs to.