Ajahn Buddhadasa was a pretty prolific writer, so if you hang around dharma circles long enough, you almost can't avoid hearing about his books. This one came particularly recommended because it dealt with the always slippery concept of emptiness, or as the translator perfers, voidness. In fact, though, Buddhadasa has not written a book on suññatā in order to treat some sort of special topic -- in his view emptiness is the very heart of the Buddha's teaching, and the only practice that really matters. At first, coming from a Theravadan, this sounds surprising. But as I've gradually learned more about the Thai Forest tradition, I've realized that the common denominator for this school is an emphasis on very open approach to the concept of 'direct experience'. Unlike the much more systematic Burmese approach which gave us the now popular notion of 'mindfulness', the Thai Forest teachers I've encountered so far seem to be much less obsessed with maps of progress, and much less prescriptive of what you should find when you look at experience.
Indeed, Buddhadasa's whole book is devoted to what you will not find in experience -- a solid and separate essential self. For him, emptiness always means emptiness of self, though he makes clear that everything (including objects we don't normally think of as having selves) is empty of self. The book then gradually unfolds level after level of how we can let go of the craving for "I" and "mine", the craving for self, that causes so much of our suffering. It's really a wonderful simplification of the Buddha's method, and Buddhadasa's writing has a sort of renegade 'cutting though' edge to it that befits a guy who headed off into the forest to escape the bullshit of monastic politics. So it's a straightforward book that you can hand to a beginner as a guide to making sense of all this emptiness nonsense. But at the same time, the topic is so deep that I'll probably end up coming back to this one again for further inspiration.