The book promises "As much practice as possible, as few theory as necessary." Some people who are after "pure practice" might be disappointed and feel cheated by this statement. There is actually quite a bit of theory, and the practice part is not going into large projects but exemplifies things with small data.
However, the promise that's only half kept doesn't matter at all, because Piepmeyer is actually right: If you understand the theoretical background, it can help you become a better practician. I've been writing SQL queries for a few years now, with no background at all. Now I've had a glimpse at the larger picture, and it's a nice outlook. Piepmeyer explains most aspects clearly and easily. Though one reading of the book doesn't mean one has really learned yet, at least there's no fear of relational theory anymore. It's the first time I read a description of a B+ tree that I could understand. And I even have a rough comprehension of MapReduce now. Thank you, Mr. author.