An inviting read, the relatively casual presentation helped me quickly digest the whole. I could hardly put it down. It works well as a partial introduction to the field of experimental linguistics, without proceeding too slowly.
Occasionally, though, the facts are obscured by the chatty tone. For example - non-nutritive sucking is a fascinating method and I admire the ingenuity of Siqueland and DeLucia for thinking it up. It unmistakably demonstrates powers of discrimination among infants. However, in discussing various cases, Boysson-Bardies allows herself to draw conclusions regarding preference as well. When she introduces the method, she explains that "monotony is the mother to boredom": the infants suck more when they recognize a change, such as from rat to cat, because new things excite them. However, babies also prefer to listen to their own name more than to others' - does this not contradict the monotony hypothesis?
One entertainment highlight is the bias against American research and American mothers, whom Boysson-Bardies portrays as simple-minded in their excessive competitiveness. She makes a good case. It is irrelevant how many nouns a kid can produce, whereas speaking freely to children cultivates the charms of conversation, and I imagine protects the parents' sanity. (You can only repeat the word DOG so many times, God help me).
The cross-cultural comparisons altogether were the most fascinating part of the book, though some of the studies struck me as too small to be reliable.