Good book. I've spotted a few small problems of English usage:
1. P. 30: The sentence "Please note that the constant 2.3 defines the type inferred by three variables, and the default keyword is a "typed" null that infers the correct type to p." The last 6 words should be "implies the correct type for p". (Even native speakers of English often get "imply" and "infer" mixed up.) (Strictly speaking, the first clause isn't quite right either since it is the compiler that infers, not the variables, but I think it is clear that what is meant is that the type is inferred by the compiler for three variables.)
2. P. 45: The sentence "The new keyword is required only for the final assignment." The word "final" should be "outer". (It might be true that it is also the chronologically last assignment, but that is not the point of the paragraph.)
Rickee