This book is a classic, so it isn't clear what I could add to available information about it. There's a reason it's a classic, and in my opinion, another printing is needed.
Stillman Drake is a recognized biographer of Galileo. This book is the product of painstaking work. It is intended for one who is interested in how Galileo arrived at his conclusions, how his mind managed to focus on relevant physical quantities and discover mathematical relationships between them. The stark departure of this process from previous "philosophical" thinking is evident from the protests of the philosophers of his day.
Drake has added a section giving brief biographical sketches of the people with whom Galileo interacted. His footnotes trace the careful research that went into the book.
-Jerome Hudson