Lately I've been studying every string theory book I can get my hands on. Unfortunately there are not very many available, so I was excited about the release of String Theory in a Nutshell written by Elias Kiritsis.
First I'll get to the bottom line. This is a well written book that should be on your bookshelf if you're interested in this topic. Its pretty clear, up-to-date, and thorough.
That being said, I have some mixed feelings about the book because it isn't what I expected. My perceptions came about from reading the first book in this series, Quantum Field Theory in a Nutshell by Anthony Zee. Zee's book is a masterpiece. Its written in a laid-back, conversational style, and it breaks topics down so well that some chapters are only a couple of pages long. I would describe Zee's book as a breakthrough in physics publishing, its a new kind of text that makes a difficult subject (QFT) far more accessible to a lot more people.
I expected String Theory in a Nutshell to be written in the same style. But it's not. The book by Kiritsis is good, but its what I would call a typical physics book with a standard presentation. Many results are simply stated with not as much explanation or derivation as they deserve in a book that I assume is aimed at a reader encountering string theory the very first time.
I've had to read other books alongside this one to follow the discussion. My conclusion is that this book is good once you've had some exposure somewhere else. I think a reader tackling the subject for the first time is going to find a lot lacking if they only read this book.
On the other hand, if you have had previous exposure, the book is a good read. It is advertised as concise-that it is. It also lives up to its advertised clear presentation. But its disappointing in that it was not written like the Zee quantum field theory book was.