This is a very informative and concise book about the world's population and I recommend it.
The main reason why I give it 3 stars is that it is a bit dated now (2022), 11 years after it was published -- otherwise it would deserve 4 stars. In fact, I was positively surprised about this book, as I wasn't sure what to expect from a co-editor of the "New Internationalist" magazine.
Importantly, the author addresses issues that are often brushed away or ignored, e.g. the fear that pension systems cannot handle an aging population. This is a real problem in developing countries or in countries which didn't have enough time to develop a pension system, such as China.
Baird did her homework and presents her data in many figures and diagrams, which make things much easier to understand than putting out data in text alone (as some other books on the topic do).
The consequences of overpopulation and climate change have substantially worsened in the last decade, and Baird is often too cautious to predict foreseeable developments. For instance, she says that China produces 4.8 tonnes of CO2 per capita (in 2009, p. 98) while it is 7.3 (50% more) 10 years later. Not entirely her fault, as she is not a clairvoyant, but these things ARE quite predictable.
My main criticism is that Baird doesn't really adequately address the environmental problems of overpopulation. Her last chapter on nature and its destruction reads like an afterthought and she quickly digresses into other areas. For me (as a biologist) the destruction of nature and the extinction crisis are by far the worst consequences of overpopulation, especially because we CANNOT "fix" extinction once a species is gone (and many will be soon). Few people seem to have this on their radar screen or even understand the complexity of it, hence it's even more important that it's pushed into everybody's mind.