It has been a while that I read Top-Rankings bei Google und Co. by Kim Weinand but it is still great. So yes, you should buy this book if you're serious about offering a solid SEO to your customers and boost their traffic!
Every time I read a book I write a summary. Here is a presentation made of my summary (german only + keep in mind that it is extremely brief and will never be able to replace the 407 Pages of the book)
Here is my Presentation PDF:
Gerne könnt ihr mir eine E-Mail schreiben bei Interesse an der ganzen Zusammenfassung.