As an author myself, I could write quite a bit about why I gave this book five stars. Let me try to keep it concise. The book introduces SharePoint 2013 in Microsoft's Step By Step Format (which walks you through common tasks from start to finish). It's definitely geared toward end users (as opposed to developers or administrators) although it's probably right at home on any SharePoint user's desk irrespective of their role. It seems targeted more toward new users and beginners however there's plenty of substance and even experienced users will find this a useful reference. I do a good bit of SharePoint development and a bit of administration so I was already pretty well versed in 2013 by the time i got this book. Development wise, I didn't pick up much (although the book doesn't pretend to be a developer's reference or administrator's guide) but I learned to do several common tasks much quicker and more directly than I otherwise would have. Outside of that, this book would serve any MS Office Power User well b/c it highlights most all of the key features provided by SharePoint 2013.
With that said, I rated this 5 stars and few books in my recent recollection deserve the five stars more than this. If you are going to use SharePoint 2013, buy this book first and save yourself a ton of time and hassle (and drastically reduce your learning curve while you're at it).
1-It's relevant - The authors did a superb job focusing on items that most end users care about most while paying less attention to more minor features.
2-It's very well structured. SharePoint 2013 is a lot different than 2010 (or any of the previous versions) particularly for end users. Because the user interface and user experience is so different, an effective book needs to get to the heart of what's changed. It does so while emphasizing how much easier each feature is.
3-It is very well balanced. I guess this will vary from user to user (after all different people will find different features more important than others) but the coverage is very well blended and balanced. The more useful a feature is and the more flexible it is, the more coverage it gets. I've been using 2013 long enough that I don't have to spend much time looking things up, but I still use this as a reference guide and I always find exactly what i want/need. It doesn't go off on tangents that are unnecessary nor does it leave you wanting for more coverage.
4-It's very well written - The author clearly knows the material inside and out. And they know how to teach it and explain it to others. There are quite a few SharePoint books on the market but this one really stands out in how well (and concisely ) things are explained.
5-It's comprehensive - Some features are simpler than others. Some are more intuitive than others. The really nice thing about how the book is laid out is that it gets you through the simpler stuff very quickly and then leaves room for the more difficult material toward the end.
6-The Layout and balance are excellent. Obviously the books focus is on text and explaining how things work. The authors use a good bit of supporting images to really drive home the points they're trying to make. Too often, images don't flow very well with the text, are located too far away from the text to really make sense or have some other type of problem. The image proportion and location really work well and the editor is to be commended.
7-It's very well edited and well written. I've been through the book several times. With some sections I've been through it 4-5 times. If I've come across a typo or grammatical error I can't remember one. Similarly, I can't think of a single case where i had to reread something or couldn't understand what they were trying to convey.
---All in all it's just a very well done book. The authors put a lot of work into it. They were extremely detail oriented and it shows. While there's much that I can compliment about it, I'd honestly be hard pressed to find a single serious negative about it. And it's not that I'm just that in love with SharePoint driving my sentiment. It's the attention to detail and editing that come together to make it a really easy, entertaining and useful read.