Here my thoughts:
Bear with me for a bit, and let's step outside of the Christian bubble for a second, and take a look at an analogy. My intent is not to offend or diminish the transforming power of the Bible, but to put the question into perspective.
Let's take the word "Christian" and put "soldier" in its place. And let's take "Bible" and put the word "Comprehensive Operational and Battle Strategy Manual" in its place.
Do think it's important for soldiers to read the entire Comprehensive Operational and Battle Strategy Manual?
It depends on the role and goal of the soldier. Yes, there are some parts that are essential for basic survival in the life he has chosen. Without those basics ingrained into him, he may face serious, life-threatening danger. There are other parts that can give insight into various situations that he may encounter, or help to process a past experience to better understand it.
But does the soldier have to read the entire manual?
What's his goal? To remain a soldier? Or to be better equipped? If he feels that he does not want to advance in his soldiering career, then he is free to not pursue reading the manual further. If he is not satisfied with where he is, then digging deeper into what's contained between the covers is a good place to start.
Personally, I'm not satisfied that I have gone as far as I have in my Christian walk. I don't think that I ever will be. Have I read the essentials and understand the basics? Yes. I believe that Jesus Christ is the son of God, came to earth, died for my sins, and rose from the dead. I believe that I have eternal life through Jesus. Have I read the entire Bible? No, there are still pages in my Bible that have not seen light. Will I ever read every word of the Bible? That's hard to say.
Will my salvation be lost if I never read the entire Bible? Absolutely not! And that point is more important than whether or not I read every chapter and verse from Genesis to Revelation.