Researchers in language development present the findings on language development from womb to 3 years to a general audience. There's so much information presented here and yet it's never dry or boring.
I picked this up because I wanted some ideas of what I could be doing with my toddler to encourage him to talk more (he clearly understands a ton more than the handful of words he'll actually say when he feels like it), but I kept reading it because I was fascinated to learn all the different skills babies acquire long before they're even ready to talk that make that achievement possible.
Golinkoff and Hirsch-Pasek break down the research at all stages of development (prenatal-3 months, 4-8 months, 9-12 months, 12-18 months, 2 chapters on 18-24 months, and 24-36 months) during the first 3 years to discuss what skills babies generally learn this period, what parents can do to encourage this development, a few fun experiments where parents can try to demonstrate these skills, and what might cause concern at this point (and just as importantly, what isn't a problem).
For the most part this is a pretty reassuring book, stressing that even before babies start talking, they're still busy learning a surprising number of skills required to make the leap to verbalizing, as well as stressing the fact that there's a wide range of ages where children learn to talk and most of the reasons children are speech delayed aren't even significant by the time they start school. As for my uninterested in speaking toddler, the book reassured me that as long as he's interested in communicating in other ways and speaks some, there's no need for concern until age 2.
As an English major in college and now a librarian, I'm definitely a fan of written and spoken language and was eager to learn about all the building blocks that go into using a spoken language to communicate. While this is written more for parents, there's enough concentration on the general building blocks of language (comparisons are made to babies learning other languages, including sign language, throughout the book) that any language enthusiast would find something to care about here.