I will not add to or argue with the specific criticisms leveled at McDonald's book, at least not those regarding the accuracy of his coverage. I don't play the King's Gambit with White (except occasionally in a blitz game) and I therefore wouldn't be in a position recognize gaps (or even actual errors) in McDonald's theoretical treatment of certain lines, etc.
However, I do own the book (and found it useful for my own needs) and have a couple of observations:
- The book doesn't even pretend to offer a comprehensive theoretical treatment, but merely presents a collection of "model games and clear explanations" to provide a "rapid understanding" of the opening. It is, and only claims to be, an annotated game collection with only King's Gambit games.
- For some reason, McDonald's book seems to more useful for someone wanting to play Black against the King's Gambit than for someone wanting to take up the King's Gambit as White. Whether this was an intentional bias (which I doubt, actually, but I won't elaborate on this) or an accidental one, this in no way invalidates it as a book of annotated games intended to provide a flavor of the King's Gambit.
I found McDonald's book useful in learning how to play the black side of the Kieseritzky, but I imagine I might find it lacking if I wanted to play the white side of the same line. And I felt the game annotations, which quite clearly favored verbal explanation over a dense web of variations, highly informative. My impression is that King's Gambit players here are maligning this book, in part, for not living up to expectations which seem unrealistic for such a book.
Demonstrable errors in main lines, of course, are another issue. Before seeing these catalogued so systematically here, I had been blissfully ignorant to the deficiencies in my King's Gambit education which have resulted from my relying on such a disreputable book....
When/if I become a serious King's Gambit player, I'm sure I will take this much more seriously. When/if that time comes, however, I hope I will still have a few non-KG friends left who will, from time to time, tell me to LIGHTEN UP!