Looks like an interesting book. I haven't read it, but it's on .
Looking at the contents, it is even more interesting that the first two chapters are on the Lotus Sutra. Why interesting? Because for a long time now, scholars have been telling us that the Lotus Sutra is not really that typical for Mahayana, despite it becoming very popular in Japan, which is the place where Western scholars and practitioners first made contact with the Mahayana.
So, I am wondering if he does a lot of "Well, the Lotus Sutra says XXX", and "because XXX is dubious, false, or whatever", that "therefore the Mahayana is also dubious, false or whatever, too". I see a lot of arguments like that around, not just in books but anywhere where such conversation may come up, which assume that all the Mahayana is summarized in the Lotus (simply because it says so). The Vimalakirti is also quite an exception, too.
So, although certain arguments can be leveled against groups that follow these sutras as foremost and paramount within the Mahayana, I don't know how much this can be generalized into the Mahayana as a whole. First though, one would have to show that the Mahayana was a "whole". And most evidence suggests otherwise. Over extension of conclusions from limited evidence and sources can be a big problem in academic studies, or, in fact, even in regular day to day discourse.
My recently moved Blog, containing some of my writings on the Buddha Dhamma, as well as a number of translations from classical Buddhist texts and modern authors, liturgy, etc.: .