The Inner Game of Music by Barry Green and W. Timothy Gallwey is one of the books I recommend above all others (well, apart from my book Practice Makes Perfect, of course). I consider that this book is absolutely essential reading for all students who have been learning for two or three years and can understand the psychology concepts contained in the book. 

It is based on The Inner Game Of Tennis originally by Timothy Gallwey. Barry Green, principal bassist with the Cincinnati Symphony for 28 years former Executive Director of the International Society of Bassists takes the concepts Gallwey applies to tennis playing and applies it to playing music. Note that this book applies to all instrumentalists, not just bassists! 

The authors help the student musician overcome some of the focus, concentration and psychological barriers that can affect performance negatively by acknowledging them and learning and practicing strategies to overcome them.

I cannot reccomend this book highly enough, whether you are a beginner, intermediate or advanced professional musician it is required reading. It doesn't matter what style you play in, or whether you are a soloist or part of an ensemble. There is something new to learn or, at the very least, a new way of looking at performance and music practice for everyone in these pages.

The Inner Game of music is available both in hard copy and for Kindle at Amazon.

You can read my full review here.