I’m glad you asked.
First, of course, the narrative is in the Bible. As we have seen, God narrates it. We know, from our study, that it is true, and that God had a purpose behind it. That purpose was for her example to be shown to others. Not every example in the Bible is a good one, of course. Some very bad people have lived, too. However, as 2 Timothy 3:16 says, every bit of Scripture is profitable to us in some way. It either helps us know what to do, what not to do, or tells us to set something right or how to keep it right.
We can see that she is a very good example. God blessed her with a child because of her faith. God rewarded that faith later. And, that faith stands as an example of how we should live our lives.
Second, it was important to explain this so you could know, in the back of your mind, why we are so thoroughly using the Bible. In a very general sense, this book is organized a little like an expository sermon. That means a sermon that exposes Scripture, so we can learn directly from the Word of God.
Finally, I hope it encourages you to read the Bible more. The Book of Acts – a history of the beginning of the church - records that the people of Berea were noble. Why? They were noble for searching the Scriptures daily, to see if the things being preached were true. (Acts 17:11) It’s important to use God’s Word as a model for living, just as the Shunammite woman used what she knew of God’s Word in her day. That is how you will prosper. However, this book is a good tool because, like a good sermon, it tries to rely heavily on Scripture to teach.