Why is the Bible interpreted in different ways?

right now im reading through the Bible to find the texts that prove our fundamental beliefs and also trying to find the texts that cause other denominations to believe in such things as abolishing the mosaic laws. ill get into that later but right now i really wonder why so many of our Christian denominations have similar and firm fundamental beliefs, but have these few differences in believes that separates our churches.

so why did God give us a book thats sometimes difficult to decode? why couldn't He have just given us a book with a straight forward message. in some cases the messages are very clear but sometimes they can be misinterpreted or even meanings can be added.

perhaps its like a test. kind of like sin or temptation. and of course overcoming those sins you need God to help you through it. in the same way you need God to help you understand the truth through the words of the bible. you need that connection with God and the Holy Spirit with you to decode the words. its like God acts like a decoder ring that you would find in those cereal boxes to decode special messages.

anyone can pick up the bible and start preaching the words, but only someone filled with the Holy Spirit can teach the TRUTH. with out the Holy Spirit, there leaves a lot to misinterpretation. so maybe God hiding the truth in the bible is a way of differentiating someone filled with the holy spirit from someone who is not.

also its a way of encouraging people to have the Holy Spirit within them.