You have to set a goal of what you want to understand and why you want to understand it, then read accordingly. If your goal is to know the usual number of eggs laid by a bird because you are trying to identify one from its nest in your yard, sure just read some Wikipedia and maybe read its sources. If you need to understand a broad topic in the social sciences in order to do your job or organize politically, well sucks yo be you, you need to spend months to years getting a handle on the various schools of thought and approaching them humbly and critically, reading many books.