The first two sections are a bit of a slog. Sacks goes into the history of educating deaf people, and he veers off all over the place into footnotes that are neither amusing nor informative. Despite that, he does manage to put the history of Sign and boarding schools for the deaf into both a historical and international context. To summarize, having successfully educated many people with Sign, demonstrating that deaf does not equal dumb in any sense, that hundred years of success was completely dismantled in favor of speech and language-focused education which returned deaf people into a second-class of people who were, truly disabled by the people supposed to be teaching them. Then, in the third section, you get people actually studying Sign, recognizing that they are real languages with real grammar and everything, and a deaf rights activism that results in the student takeover at Gallaudet. That part is interesting, not least because the recognition of a language really seems to lead to recognition of culture in both the ethnic sense (Welch or Gaelic, say) and in the human-rights sense (reclamation of the words "gay" and "black" as part of an ongoing battle to receive the full human status to which all people are entitled.
There is also some interesting stuff on accommodation and mainstreaming which parallels more recent educational efforts demanded by people with autism. I really wish there had been some sort of update, though, because the book was published in 1989. Fortunately, the Internets were able to bring me up-to-date.