There is a huge difference between casually reading the Bible and studying it to get the most benefit out of it. Both have their place, along with other disciplines like memorization and meditation, but your devotional diet needs to be balanced.
Reading books on the lives of powerful Christian leaders is useful. It gives you an insight into how their relationship with God developed; how He revealed His will to them and gave them the opportunity to achieve greatness through His inspiration - but it's not the only resource.
Within the pages of your Bible, there are accounts of how the same God who lifted us up out of a directionless life worked within and through ordinary people to achieve extraordinary things. A skilled expositor can help flesh out and personalise those stories, unlocking details you may have overlooked, demonstrating practical applications that have the potential to transform your life in the same way.
Instant success may not be guaranteed. But spiritual growth is. However, certain specific keys will help you get more out of studying your Bible:
Book studies on the following books of the Bible: