Achronim discuss whether krias haTorah is a chovas hayachid which can only be fulfilled in the presence of a tzibur or whether the chiyuv is on the tzibur as a whole. The nafka minah would be whether an individual has to make an effort to find a tzibur to listening to layning. If the chiyuv to listen to kriah applies to the yachid, the answer would be yes, but if the chiyuv is only on the tzibur as a whole, a yachid who does not find himself in a tzibur for krias hatorah has no obligation to do anything. Those who have gone to YU know that when the Rav used to commute from Boston to NY he would sometimes miss krias hatorah and gather a minyan in yeshiva to fulfill the mitzvah.
The first Mishna in Megillah tells us that villagers may read the megillah early on the 11th, 12th, or 13th of Adar which fall on Monday or Thurs., the days when the villagers traditionally gathered together in the cities. What were these villagers gathering for? Rashi writes that Monday and Thursday were the days when court was in session; the villagers came to the city to do their legal business. The Ran, however, writes that the villagers gathered in the city on those days because those are the days in which krias haTorah is done. Apparently the villagers did not have a minyan (or perhaps did not have a sefer Torah) where they lived and needed to travel to a central meeting point to fulfill the mitzvah of kriah. R’ Shternbruch in a number of his seforim points out that perhaps the point of disagreement between Rashi and the Ran (whose explanation is echoed by most Rishonim) revolves around how to understand the takanah of kriah. If kriah is a chiyuv on the tzibur as a whole, then where no tzibur exists, such as a village, there is no chiyuv. But if there is a chiyuv on the individual to hear kriah, then we understand why villagers which otherwise did not have a tzibur would nonetheless gather to create one to fulfill their chiyuv.
I should point out that the Ramban in Milchamos (first perek of Megillah) seems to indicate that krias hatorah is a chovas hatzibur; read more about it on Chaim Markowitz’s blog here.
And while on the topic, just to mention it again (previous post here), if krias hatorah is a chovas hatzibur, then it is hard to understand how a second leining of parshas zachor can be done just for women. Women cannot form a tzibur, so how can the chiyuv of kriah be fulfilled for them in the absence of a minyan of men?