Need a good study book for 500 ton master

Hi Captain Lee

        I just took my 500 ton master license, but did not do well. I've been studying with a study guide by Captain Joe. His web site is Is there any other study guides that could help me more to try to understand what I am reading. Thank you for your time. 

          Captain John

The Murphy books are good. Taking a prep course also gets you in the right frame of mind.