No, you shouldn't lie to your grandmother—but neither should you simply leave your Bible on the shelf! Yes, I know you're very busy—but even reading it five minutes a day could make a surprising difference in your life.
After all, have you ever asked yourself why your grandmother gave it to you? I suspect she did it because the Bible has been very important to her over the years and she knows it could help you also. The psalmist said, "Your word is a lamp to my feet and a light for my path" (Psalm 119:105). This has been the experience of countless people through the ages, and your grandmother knows it could be your experience as well.
In spite of what you may think, however, the Bible isn't just for old people! The Bible is timeless because it deals with the basic questions of life: Who am I? Where did I come from? Why am I here? Where am I going? How should I live? What is God like, and what difference can He make in my life? Nothing could be more important than discovering God's answers to these questions.
I suggest you start with one of the Gospels (such as John). Even if you read only a paragraph or two each day, God can use it to point you to the greatest person you will ever meet: Jesus Christ. God gave the Bible to us because He loves us and wants us to come to know Him. May this become true in your life.