In Job this is particularly important because it yields a hint into the overall meaning of the book. As we begin we have the most well-known portions of the book. Through a glimpse into a conversation between Satan and God we come to find out that Satan will have permission to bring a testing against Job to try and prove that people are only faithful to God if prosperous. After an unsuccessful attempt to prove his point Satan returns to gain further permission to afflict Job personally. Interspersed in the scenes is an account of the calamity that comes upon Job. The particular portion is short and to the point and moves the reader quickly to the main portion of the text which is the cycle of conversations to follow that involve Job and four friends who have come to "comfort" him.
As you move into the conversations, you as the reader have an advantage in assessing what is going on (which is what you should be doing as you read the conversations). The three friends will be making attempts to tell Job why this has happened to him and you have information that they do not. From the very introduction of the book in this manner you can know one thing, the calamity that comes upon Job is not God's judgment on some particular evil in his life. Much is said and dissected in regards to the introduction, but this seems to be the main purpose: to give the reader a different perspective than the characters in the text so that you can see how wanting their arguments are. In my best assessment, the overall message of the book has something to do with showing the difference that a little piece of information can make.