When I was going to read this book, I expected some sort of advertising book for his own brand. But I was wrong, it is an interesting read.
Ries refers a lot to his own company called IMVU, which provides instant messaging services where people use avatars to communicate. He does not only refer to his success, but also his failures, which makes it even more interesting. The book evolved out of his experience as an entrepreneur and is a good inspiration for starting your own business the lean way.
The main idea is to start experiments as soon as possible. Start testing with real customers at a very early stage. Ries suggests to go out with the product, even if it is not finished. Doing so, you can evaluate every every aspect of your business within real live, which is so much more valuable than any theoretical analysis in strategy, marketing and product development. Possibly even start testing different versions with different customers groups as soon as you can and continuously improve on the results.
Eric Ries has written an awesome book. If you want to start a new business, this is a must-read. It provides a lot of real live examples, on how to make a startup successful.
It is not a handbook, not some kind of how to grow your business. But it serves very well as an inspiration and motivates to work out something new.