The title of the book is misleading. It is not about compassion and not especially about Upaya or skilful means. These topics are however touched on as regards to the title at the preface area.
This book is really about what Buddhists believe in or not as the case may be, pointing out that what appear as metaphysical statements in most strands of Buddhism, are little more than skilful means, designed to fulfil an objective but not to be taken as concrete propositions.
The Buddha said that his teachings were a raft to enable getting across and not to be clung to. However, the Theravada school appears to have developed a highly elaborate metaphysical system of mind or Abhidhamma, and this book leads us through criticisms of this approach illustrating this through Buddhist philosophies such as by Nagarjuna and the Vimalakirti Niddesa. It then takes you to Mahayana and Zen approaches which expanded the role of skilful means and absolute vs conventional truth.
The book is modest and provides excellent vignettes and tasters of samples of Buddhist teachings through the spectrum of its development and evolution. One highlight is the description of the arising and ceasing of mind moments contrasting the essentialist school with the "only the present is real" school. This lends itself to descriptions of such concepts as Emptiness and non-duality. It is however clear that some of these contrasts are based on a simplification of what were a train of arguments and teachings through a host of groups of which the evidence is substantially lost. An important point the book makes is that unlike Western philosophy, Buddhist philosophy can not be divorced from a soteriological function.
This book is not very conclusive and seems to leave the reader to work it out for himself. It is clear from the writing that the author is not an expert on early Buddhism and that his sources are sometimes secondary. Buddhism did not avoid taking up a position, but this "position" was ultimately dependant on the mind of the disciple. Anathapindika, an early disciple when asked what his view is says: In so far as views are impermanent, I see the danger in them and see the higher liberation. In other words, views have their place (though not dogmas or fixed views) but they are secondary to the arising of wisdom and the cultivation of the path by an evolving mind which needs guidelines to begin with. Eventually, the practitioner may see beyond views.
Having said this, by rubbing in Upaya as the essential teaching of Buddhism (or position), one is falling in to the trap of views. The Buddha did say: What do I teach? Answering with the 37 factors of enlightenment to more simpler summaries. Schroeder certainly makes a virtually unassailable case in chiselling out a rather slender and packed volume.
Above all I congratulate him for helping one to think and exposing one to some excellent quotations, but like Shroeder I say, this is not the answer, we're still looking.