Joanna Penn is certainly an expert on writing, having published many fiction and non-fiction books (including many on writing and publishing), and her take on productivity is a worthy one. She writes in a conversant and approachable manner, and formats the chapters in a way that helps the reader digest information. I should note, however, that this is a short book, with only 89 pages of content (in the ebook version).
As a professional organizer and productivity coach and as a professional writer, I'll admit that I was disappointed in the brevity of the book. I could definitely recommend it for the shelf of any beginning author and for authors seeking general guidance on productivity. It is not a complete solution, though, and is really designed as a primer on productivity for authors, rather than a deep dive. Anyone with ADD or ADHD, or with more complex focus, achievement, or productivity problems would be well suited to peruse this book, but then seek more specific, and perhaps more personalized, guidance.
Pen focuses the majority of the text on strategic issues (setting and meeting goals and deadlines, delineating the difference between important work and busy work, and setting boundaries). There's one specific chapter on "Making the most of your writing time" which, if fleshed out, could have filled fifty or more pages rather than seven.
Penn provides solid material on specific productivity solutions (dictation, outsourcing, and productivity tools) as well as a chapter on collaboration, which is pitched as a productivity solution; of course, collaboration invites its own productivity drawbacks, and she briefly advises on tactics to make it productive. (Granted, Penn has written an entire separate book on collaborative work, and one suspects there is more granular advice to be found there.) Finally, the book's central content has sections on mindset and creating healthy habits as a writer, all of which would prove useful to beginning authors and nice reminders for the more experienced.
The remaining pages (fewer than thirty) provide a detailed bibliography of all the books Penn quotes and cites, as well as a nice recap of all of the end-of-chapter questions to help prompt the reader to his or her next steps. Penn has also included an excellent list of all the resources and tools she's references throughout the book, with links and technical guidance.
I know from listening to Penn on her podcast and reading her articles and some others of her books that she is a font of wisdom. However, I admit to being a bit disappointed by the lack of depth in this book. I was hoping for suggestions with which I was unfamiliar, or material that could help help the adrift or drowning reader further with more step-by-step instruction. For example, in the second-to-last chapter, on author mindset, she makes a passing reference to getting an accountability partner to overcome the guilt of not writing. True, but the "tool" of an accountability partner is so central to productivity, especially in creative endeavors, that (for readers unfamiliar) it would have been a boon to have much more material explaining how to find and make use of one.
Short review: good material, but it could have been much more detailed. Penn has much more wisdom on this topic, and I wish she'd gone deeper.