For some reason I haven’t had any free copies of books to review recently; maybe the market for tech books has finally collapsed with AI? Books are still being published though and luckily, as someone who once published a book via an O’Reilly imprint, I have a lifetime subscription to O’Reilly online learning which gives me free access to all the tech books I ever need. Two books were published in the last few months that I was curious to read: the third edition of “The Definitive Guide To DAX” by my friends Marco Russo and Alberto Ferrari, and “Microsoft Power BI Visual Calculations” by my colleague Jeroen ter Heerdt, Madzy Stikkelorum and Marc Lelijveld. As I’ve said many times, I don’t write book reviews here (least of of reviews of books by friends or colleagues where I could never be unbiased), but I think there’s some value sharing my thoughts on these books.
“The Definitive Guide To DAX”, 3rd Edition
It’s generally accepted that the one book that anyone who is serious about Power BI should own is “The Definitive Guide To DAX”. If you don’t already own a copy you should buy one, but since most people who read my blog probably have one already the more interesting question to ask is what’s new in the third edition and whether it’s worth upgrading – especially since I’d seen Marco say that the book had been completely rewritten. I’ve heard the “completely rewritten” line before and I was sceptical but it turns out that it really is a very different book. It’s not completely rewritten because there is material there from previous editions but there are a lot of changes.
First of all, as you would expect, all the new additions to DAX since the second edition was published are covered including user defined functions, visual calculations, calendar-based time intelligence functionality and window functions. These are all really important features you will want to use in your semantic models and reports so this is the main reason you’d want to buy a copy of this edition.
Secondly, the main (and justfied) criticism of the previous editions was that they were, as we say in the UK, “heavy going”. They had absolutely all the information you would ever need but they were not the easiest books to read or understand. That has been addressed in the third edition: the tone is a little bit more friendly and difficult concepts are now explained visually as well as in text. As a result it’s easier to recommend the book for beginners.
Thirdly, some advanced topics (for example around performance tuning) have been dropped. For example I searched for the term “callback” in this new edition and found no mentions; that’s not true of the second edition. I have mixed feelings about this because it means the book isn’t as “definitive” as it used to be, but I can understand why it’s happened: with so much new content to add, keeping these advanced topics would have made an already long book too long. And let’s be honest, how often do you look at the details of a DAX query plan? If the aim is to teach DAX then cutting content means it’s easier for the reader to focus on the core concepts.
In summary, then, another great piece of work from Marco and Alberto and worth buying even if you have a copy of an earlier edition.
“Microsoft Power BI Visual Calculations”
A whole book about visual calculations? As I mentioned above, they’re covered in one chapter of “The Definitive Guide To DAX” but that book focuses on DAX; this one takes more time to explain the concepts and, crucially, includes a lot of practical examples of how to use them. Like user-defined functions, when visual calculations were released there was an explosion of community content showing how they can be used to solve problems that were difficult to solve in Power BI before – problems that no-one could have been anticipated that would be solved with visual calculations. The real value of this book is showing how to build a bump chart or a tornado chart with visual calculations and that makes it worth checking out.
Closing thoughts: why buy a book?
As you would expect, a lot of the information contained in these books is already available for free somewhere on the internet. And with AI you don’t even need to know how to search for it or stitch it all together – you can ask a question and get an answer customised to your exact scenario. So why buy books any more? I guess it depends on whether you only want to get your problems solved or understand how to solve problems yourself. For me (even though my attention span has eroded in recent years, just like everyone else’s) the only way to grasp really difficult concepts is through long-form written explanations or training courses, not fragments found in blog posts or 10-minute videos. I suspect that AI is the final nail in the coffin of the tech publishing industry but the tech book industry not being viable any more is not the same thing as tech books not being useful any more. Or maybe I’m just old-fashioned.
Thank you for the comments about the book!
The decision of dropping the chapters about the optimization part is intentional and unavoidable: we had to add more content to cover UDFs, calendar-based time intelligence, window functions, and visual calculations, and we have another 800-page book just about optimizations. Because no publishers on this planet would have allowed us to print a 1,600-page book or to create a Volume I / Volume II series, we released Optimizing DAX as a separate book.
And to be really “definitive” we should also add something about data modeling, relationships, and… well, you know how this ends!