I am not sure if the author did this (he certainly doesn't mention it), but a lot of what constituted Watson at the time of Jeopardy was published as a set of 17 papers called "This is Watson" in the IBM Journal Of Research and Development.

Other than that too, I think you can make a reasonable assessment of any NLP system at this level of abstraction by looking at what is cutting edge in NLP today (by following conference proceedings etc).