This is a wonderful book! The author does an excellent job creating an interesting biography that flows well and helps the reader understand the life and spirituality of a truly amazing Saint.
This book is based on St. Faustina's diaries. However, where the diaries are massive and don't always flow in a way that is easy to digest [they are not chronological], this biography organizes the diaries and what they contain in such a way that it is easy to read without losing any of the authenticity of what Saint Faustina wrote about her life and her relationship with Christ.
In addition to a really fascinating story, this biography is great spiritual reading. I knew a little about St. Faustina and the Divine Mercy devotion before I started the book, but I have found her life to be extremely inspiring and I think I have had a lot of spiritual growth reading this book - coming to understand Divine Mercy and to understand what Sister Faustina went through to bring it to us - wow. Its just amazing.
So, I highly recommend this book both for your reading enjoyment [its a great story!] and for your spiritual edification! You can't lose either way. :)