Having read other books by Sacks, I found this something of a disappointment. He seems to jump too rapidly between different areas - a bit of history, a bit of applied linguistics, a bit of politics. Coupled with the fact that many of the pages are dominated by footnotes, this results a book which is difficult to read. Sacks became aware of the poor deal the deaf have been getting in our society - essentially being denied the use of their own language - and wanted to get this message out to a wider audience. However, in his enthusiasm for the cause, I feel Sacks has not given sufficient consideration to the readability of the book. That said, if you are not put off by the way it is laid out, then you will find much of interest in the book, for example the account of the students' strike at Gallaudet University (where Sacks does stay on one topic for a decent length of time).
In principle the argument is straightforward. Children need to learn a language at the earliest possible age and in the case of deaf children this means a true sign language, rather than spending years learning to deal with spoken language or a signed version of it. However in practice the parent of a deaf child will have some difficult decisions to make. I felt that Sacks didn't give sufficient attention to this, and in particular didn't distinguish this question sufficiently from the problems of young deaf adults in our society.