A pretty decent introduction to the Apache Spark analytics engine. Good examples, nice code samples and an absolute minimum of screen shots (which belong in blogs, not books in my opinion). I'm not sure it really needed code samples in both Python and Scala, since the samples were generally very similar, but I assume some people found one or the other more readable (the Java code samples however were often different enough to warrant being included).
The end of the book didn't feel as necessary as front three-quarters, with the data lake chapter coming across more like an ad, and the chapters on Machine Learning seemed rather specialized for a general introduction -- if you're going to include material like that, why not GeoSpark instead, which I at least would have found a lot more interesting.
One misfeature in the book is likely the fault of the publisher: Almost all of the references in the printed text are shortened URLs pointing to the publisher's website. No doubt the theory is this protects against link rot. Alternatively, it replaces one possible source of link rot with two. There are standard formats for citations of hyperlinks. That would have been considerably more appropriate in a print edition. (Although it is interesting to see a case where the print, not digital, edition is the poor cousin.)