Reddit reviews Guitar Zero: The New Musician and the Science of Learning

http://www.amazon.com/Guitar-Zero-Musician-Science-Learning/dp/1594203172

Check out the book Guitar Zero. It's by a cognitive psychologist who, at almost 40, decides he wanted to learn an instrument. It goes into his personal journey as well as a lot of info and studies about how humans learn things in general.

I started at 40. It's a journey, your journey. Enjoy the trip.

Also read Guitar Zero. This was written by an older learner who views his skill development through the lens of cognitive psychology. It is a great companion for those of us who began later in life.