The review linked above does an excellent job of summarizing the book's strengths (and few weaknesses). Here I'll comment on its utility from my perspective, that of a Class player who has used the English for a number of years.
For a general survey and one-volume treatment of the opening, I still rate Nigel Povah's How to Play the English Opening as the most useful book I've read, although it's out of print. This makes McDonald's work probably the best single-volume introduction currently available. At 190 pages, it's significantly longer than the Povah book and also somewhat longer than most other Starting Out series books (including McDonald's Dutch Defense volume). That said, it is by no means comprehensive and someone who wants to play the English will have to obtain supplemental book/DVD resources or do significant database research to flesh out their desired repertoire.
The general strengths of the Starting Out series are on display in this volume, where the author takes a significant amount of space to explain important ideas for both sides at key points in variations and often points out why superficially attractive moves do not work in some concrete variations. This presentation of the typical plans for both sides - in the process showing a balanced perspective regarding evaluations of different lines - is what makes the book most valuable for me, especially since the Povah book did not cover some of these ideas, particularly in the Symmetrical lines.
For those interested, here's a more detailed breakdown of the perceived utility of the various chapters.
- Symmetrical English 1: Black's Kingside Fianchetto. This was probably the most valuable chapter for me, since I have had little practical exposure to, or understanding of, the Symmetrical variations in general. By coincidence, I played a recent tournament game in one of these lines where I had gone out of my own book at move 5, so this section helped plug a large hole in my repertoire. The example games I thought were particularly well-chosen to illustrate White's plans.
- Symmetrical English 2: Early Action in the Centre. I was able to largely ignore this chapter, since my chosen repertoire doesn't feature these variations. However, I was careful to look at certain variations that Black could use to ensure they did not pose a threat.
- Symmetrical English 3: The Hedgehog. This chapter discusses a complex position-type that can also arise from other openings such as the Sicilian. It features deep maneuvering and relatively few tactics, although one has to keep some possible tactical points in mind along the d-file especially. I found the discussion of both sides' ideas to be quite valuable, although the complexity of the variation and some of White's move choices are not treated in depth.
- The Nimzo-English. The main line with 4. Qc2 is what I play and is looked at only on a superficial level. Given that the basic ideas in the line are positional and not terribly complicated, this is forgivable. More space is allocated to the tactical Mikenas Attack with 3. e4 (in place of the normal 3. Nf3) and the 4. g4 attacking thrust. I appreciated the author's evaluation of the greater danger for Black in the latter two lines, as well as his explanations of White's ideas, and may look more closely at them in the future for my own use.
- The Four Knights (including the Reversed Dragon). The author's presentation of key lines matched up well with my own repertoire with 4. e3, which has been extensively researched due to the common nature of the variation at the Class level. However, in general the coverage of the alternatives to 4. g3 was superficial, with only one response (4...Bb4) to e3 presented.
- Black Plays a King's Indian Setup. This was the second most valuable chapter for me, introducing some key late opening/early middlegame concepts and exploring the different alternatives for White to meet Black's basic kingside attacking plan. The variations covered here also tend to be commonly encountered in tournament play, so are important to study; Annotated Game #12 is a good example of this. I found the chapter title to be somewhat misleading, however, as it doesn't really cover a "pure" KID setup against the English. In contrast, Povah's book distinguished between the two, having a separate short KID chapter and placing these variations in a chapter entitled "Closed Systems II" because they typically begin with 1...e5 and feature Black's knight developing to c6.
- Reti Lines. The author gets significant credit for including these lines, which White can use against a Slav or Queen's Gambit Declined setup and which are often reached via the Reti Opening (1. Nf3). However, the lines are only shallowly covered from White's perspective and are probably more useful for Black players for study purposes. Nevertheless, this is a neglected area of the English and helps fill in a White player's repertoire, avoiding the idea that White should simply transpose to the main lines of the QGD or Slav with an early d4. (Perhaps this is a good idea for d4 players to avoid certain Black move-orders in these openings, but for the English Opening player this would mean studying a lot more theory.)
- Other Variations. The author usefully touches on the Dutch and Grunfeld setups for Black and how White can (and should) vary from the usual queen pawn opening ideas. Other irregular responses are mentioned as well (for example 1...b6 and the sequence 1. c4 e5 2. Nc3 d6) and some basic ideas given, but players will have to do their own homework on specific variations.