There is no single greater theologian/pastor in the world today than Dr. John Piper. I’m sure that there are equal, if not greater, theological minds than his. However, there is no one that I know of with the ability to communicate deep truths like Piper. I would challenge you to visit his website by clicking the link above and learn from him. I guarantee that there will be many things that you will disagree with him on. I also guarantee that there will be many other topics that will really make you struggle; but I also guarantee that he will justify every one of his positions with copious amounts of scripture.
If you are really interested in stretching yourself you need to order a copy of his sermon, “Is God less glorious because He ordained that evil be?” It will revolutionize your view of God. You will walk away with a higher view of God than ever before. I would dare say that it may be the single most influential sermon that I have ever heard. I’m in the process of listening to it for at least the fourth time!