I found this book extremely useful, it's hands on guide for all aspects of online marketing for musicians. It has very well structured, well informed and easy to follow advice that you can follow step by step.
I used this text for my dissertation studies at University, it covers a great deal of information, accurately and on a easy to understand basis. I found the digital social media topics very useful and was great evidence for my study.
The fact I could have it in kindle format, online instantly was very helpful as I could take it everywhere I went, wherever I was to study - thank you!