For those interested in, doing research on, or teaching about food security, Mark Gibson's "The Feeding of Nations: Redefining Food Security for the 21st Century" (2012) is an essential reference to have. The book is a hardcover 640-page academic work, and unfortunately not cheap. There are a couple of ways to access the ideas if the cost is a barrier, one is via Google Books, which offers some parts, and the other is on the archive of a discussion Mark lead on the FAO's Global Forum on Food Security and Nutrition on the topic of food security. I was fortunate to find a used one.
In many parts, the book is a high level review, such as its overview of nutrition and malnutrition, and is not ground breaking. But, as a reference book for important considerations related to food security, this is one of the few places that attempts to bring it all together. However, in other parts, it is quite detailed, such as the history of food security related concepts. Unique to the book, I believe, is the inclusion of a wide range of topics, often covered in topic-specific books, including linkages to: agriculture, forestry and fisheries, science and technology, socio-cultural aspects, natural resources, health and nutrition, governance and politics, etc. The author also offers thoughts on redefining food security for the future.
There is a downside to an author who has been thinking and writing about a topic over such a long period of time – the references and content can be recycled and get dated. For example, some sections are largely cited from works published in the early 2000s (2000-2004 period), and it is clear that some parts were first written some time ago, even if published in 2012 (e.g.: "it was once again recently reaffirmed at the International Scientific Symposium on Measurement and Assessment of Food Deprivation in 2002", page 16). I suppose "recently" could be a relative term. Nonetheless, a recommended reference work on food security – particularly for those seeking a key resource on the topic, or those looking for relatively condensed and readable content for undergraduate students.