The original GTD is a modern masterpiece of its kind. Well paced, focused on details and intensely practical with just enough theory to put Allen's simple yet unique system in context. His second book, "Ready for Anything", had less immediate appeal and direct applicability but grows on repeated reading, providing more insights behind the basic processes of GTD. I keep both books to hand and dip into them frequently, and they have had a profound impact on how I now manage my work and life.
In trying to make "Making It All Work" a stand-alone volume, David Allen ends up repeating, in some cases less pithily, too much of the earlier material, and there are extended passages that are little more than a rewording of the original GTD book. This new book does provide a broader context and an enhanced perspective on the GTD system, and makes the system fit together more neatly along the two dimensions of control and perspective, although these two dimensions were evident enough in "Getting Things Done". For that alone, the book is worth reading, especially for GTD advocates looking to obtain further insights into the system (although members of GTD Connect, the GTD community, will be familiar with most of the material). I am sure it will provide further value on additional readings.
That said, there is relatively little new ground covered here. There is some fine tuning of earlier terminology, but this smacks rather too much of mere relabeling. Collection becomes "capturing", processing becomes "clarifying", reviewing becomes "reflecting" and doing becomes "engaging". The new terms sound more sophisticated but I feel the original terminology was more concrete and to the point.
The "six-level model for reviewing your work" is now the "Horizons of Focus". This phrase has been adopted in David Allen's materials for some time now, but does not quite jive for me as: 1) "horizons" for most people convey horizontal distance, rather than the altitudes that these "horizons" refer to (30,000 ft, 40,000 ft etc.). In adjacent paragraphs he refers to "upper altitudes" and "elevated horizons" -- some mixed metaphors here; 2) it again suffers a little from being rather abstract, which the original GTD book largely avoided.
Perhaps tellingly, the original "Getting Things Done" was seen to focus primarily on the "getting control" dimension of self-management. "Making It All Work" again spends 125 pages on "getting control", double the 65 pages on "getting perspective". I had hoped the latter would have received more space and attention in this new book.
I also find the style in some places too long-winded, in a couple of cases inappropriate (does the phrase "anally retentive" really belong in a serious management book?) and the terminology inconsistent (his twenty thousand foot level refers to what he calls "Areas of Focus". However, while this appears to be the standard phrase, he also refers to it as "areas of responsibility and interest" and "areas of focus and responsibility", the latter in the title of a chapter. The use of title/heading styles also does not appear consistent, which makes the structure of some sections a little difficult to follow. In some places he also repetitively redefines terms he has already defined earlier.
None of these stylistic issues impact the meaning or the value of the underlying concepts, but leaves one wishing the editor had spent more time tightening up the style and terminology, as they do detract from the reading experience. "Getting Things Done" was solid in this respect. Terms are clearly and concretely defined and then used consistently, without unnecessary stylistic variations.
It is still necessary in my view to read the original "Getting Things Done" to get the the most of this book, which is primarily a useful companion volume, an elaboration of the earlier book's key concepts and frameworks and a refresher for those interested in Allen's ideas and methods.