In our opinion Carcassonne is one of the easiest (adult) games to learn. Even though, the strategy aspects of the game is quite sufficient, it is not achieved by adding a lot of rules for strange cases. The game has very few rules that you have to learn. It takes about 5 to 10 minutes to learn the basics/rules. After that point, its simplicity allows you to develop strategies to defeat your opponents.
Game time for 1 round is also very shorter than other strategy games. It usually takes around 30 minutes to finish a round of basic game without expansions. This of course can increase if you start thinking a lot. But unlike other strategy games, you don't usually plan for a long run since your plans usually change with every tile you draw and every time someone makes a move. Thus, you need an overall strategy but you must observe the game closely.
The basic game, without any expansions, is pretty strait-forward and and number of different game play elements, such as special tiles and followers. are relatively small. Yet, this does not mean that the game is limited or boring. That being said, we should also emphasize the effects of the expansions.
You should know that most of the expansions are very interesting and adds a lot to the game. Some of them, such as The Princess and The Dragon, will not only add new tiles to the game but also introduce new types of followers and creatures. Interestingly, adding more expansions does not increase the complexity of the game that much. However, they significantly increase your strategic opportunities. For example, you may choose to focus more on the farm tiles when you include the "Traders and Builders" expansion or you may worry more about the roads when you include "Inns and Cathedrals".
Another beauty of the game is being able to include as much expansions as you wish. They are designed to work well with each other and your options grow exponentially with every expansion. However, adding expansions increases the time requirements of the game. Because with every expansion, you add significant amount of new tiles. There are currently 9 full expansions that alter the game almost completely and almost 20 mini expansions that add fun features or small changes. These mini expansions are usually introduced with special pack and may not be purchased on their own. So don't worry if you can't find them anywhere.
Another factor that affects the play time of Carcassonne is the number of player. Although you may think like the game will end sooner with more players, in our experiments we experienced a significant increase due to the in-game politics. Usually, every player has his own territory and self growth plans and this yields more conflicts and opportunities. Yet, you don't need a lot of friends to fully experience the game. It is also extremely satisfying even when you are only 2.