Nicolas Darvas was a professional dancer who became interested in the stock market. Because his professional job meant he travelled the world he became reliant on information that was mailed to him. He would scour Barrons Weekly for stocks with unusal volumes and when they 'broke out' of their 'box', he would buy.
His technique was in essence a breakout strategy, buying when levels of resistance became levels of support.
For me, the book delivered 3 very important lessons.
1. You need to develop your own system through trial and error and hard work
2. Scaling into positions is key (and an incredibly tough skill to master)
3. If you find a successful formula, stick with it and reap its rewards.
If you want to know the technical details of the 'Darvas Box' method, then you are probably better off searching the internet for free information - In fact you can download the Darvas box method for Tradestation (for free) and use it in your trading, however if you enjoy a well written success story that reinforces (or introduces) some basic tenets of trading, then buy this book.