No, I don’t think God is going to be mad at you if you don’t read your Bible, but He is going to be sad, because He won’t have the opportunity to have fellowship with you through its pages and become your good friend.
Think of it like this. Suppose you want someone to be your friend (and they want to be your friend also), what do you have to do? You have to spend time with them — talking with them, listening to them, and just getting to know them. And in a far greater way, the same is true with God. He loves us and wants to be our friend, but that means we need to get to know Him by talking to Him and listening to Him.
That’s why the Bible is so important, for it is God’s written Word, given to us so we can listen to Him. In it He tells us about Himself, and also how He wants us to live. The Bible says, “All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness” (2 Timothy 3:16).
Don’t be intimidated by the Bible’s size, or by anything else about it. Instead, begin by reading a small part of it each day. Start, for example, with a few paragraphs from one of the Gospels, or from Psalms (and in a translation you can understand). Read it carefully, thoughtfully, and prayerfully, asking God to help you understand it and apply it to your life. God will bless you through it.