There is some benefit by listening to scriptures by Mp3 or CD, especially if you are time-crunched. I have listened to them during my commute at times. It gets you thinking and reinforces lessons from the scriptures. When it comes to reading the scriptures there is nothing wrong with repetition. Each time I read through them they are different. Something else stands out prominent depending upon where I am in my life. While the words never change the meaning and application is ever changing and evolving.
If you want to do deep study this is probably not the best method. You could with some effort. As you are listening take notes on anything that stands out you want to explore deeper.
Bottom line - any scripture study is better than none.
Each method of study has it benefits. I have a 30-minute round-trip commute to work and back each day, and have listened to the Book of Mormon during that commute for seven years now. I'll bet I've listened to the BoM between 15 and 16 times during that time period. While I can't do intense study while listening, I have gained other blessings. I find myself able to quote verbatim a great deal of the Book of Mormon, because I've heard it spoken over and over. The sheer repetition has given me a depth of understanding in many areas that I haven't ever achieved reading. I especially have been blessed with a deeper understanding of the "Isaiah chapters." I wouldn't give up my audio BoM for the world!
Edited: TheQuietMan on 27th Apr, 2009 - 12:25am