I decided to reread this now that I've had the chance to write many of the kinds of poems that are portrayed in this book.
What makes it ingenious is the same thing that, at times, can make it tedious to read. Holllander uses poems that he created to show what the effects of the sounds of meter and rhyme will do to the poems in which they are used. These examples are incredibly helpful to those who are unfamiliar with traditional poetic meters, but I wouldn't say this is a book for the novice poet. On the contrary, the whole point is that small matters within the poems themselves are what can make them successful or not, and I'd wager that such particulars (which, in effect, can alter pacing, mood, and interpretation) are not the first issues that new poets are concerned with.
Hollander also gives examples from other poets at the end of the book (this is in my copy, which is only the second edition; I believe at least two more editions have been released) who have written well-known sestinas, ghazals, rondels, and other forms of formal verse. Since the aim of the book is instructional, it probably should be saved for those who actually want to try writing such poems. Otherwise, free and accessible means of reading about these kinds of poems can be found online for the non-specialist.