This book, written by a linguist at the University of Hawaii, is a good introduction to current academic thinking on children's first-language acquisition. It is not intended as a guide for parents, per se, but is usable for parents interested in this aspect of their children's development (there are occasional interjections to the effect "not to worry"). It's written in a very clear style with a very logical arrangement, without jargon drawn from linguistics. The discussion is limited almost entirely to an English monolingual environment, and does not go beyond early childhood and the acquisition of the local basic grammar and vocabulary.
The author starts by examining how children learn the meaning of words in isolation and how sentence structure and other elements of grammar appear to be acquired. Only in the second part does he explore phonology; with good grounds for the general reader, as this involves considerably greater abstraction. Thereupon some sociolinguistics appear, in the context of differing parental behaviors. Finally, the author discusses abstract models of human language as they bear on language learning; is the language learning facility a separate brain function, unto itself, or is it just an extension of other parts of human mental equipment? All of this is discussed in the clearest and most concrete terms.
Brief appendices include the International Phonetic Alphabet as it is used in the book and some tips for keeping diary-style records of a child's languistic behavior and progression. In this context I might mention that the single "how to/how not to" element occurs in the author's discussion of "re-casting"; does adult repetion of children's statements, in standard grammatical format, correcting deviations from local norms, help children acquire these norms? The answer appears to be "no".
A minor quibble: when referring to children by pronouns, the author randomly switches between "he" and "she" when sex is not at issue. When parents are referred to, the author inevitably uses the word "mother", in which case sex could conceivably be an issue in terms of linguistic usage or other behaviors. It would have been clearer in my opinion if the author had followed what is current colloquial English usage and said "they, them" etc. If parents are meant, say "parents". But this sort of thing is common in writing in academia, even when the audience consists of non-academics, as in this case.