The title quotes A. Damasio from the front cover.
In my view Gerald Edelman has the best theory of consciousness there is, by far. It is strongly grounded in biology, evolution, the nature of the brain and nervous system. Firstly, consciousness is not a thing, it's a process. Consciousness is private, unified, and informative. It is private because no two are alike and its workings are dependent on its own history. It is unified or integrated because it arises from a variety of sources, e.g. the different senses and a body which provides a built-in value system. The unified integration is the result of global, reciprocal mappings among diverse groups of neurons. It is informative and highly differentiated because of these various sources.
Conscious awareness arises from a lot of unconscious processing, along the lines of information theory (a branch of mathematics) with importance to the organism driving what is selected.
Edelman holds there are two levels of consciousness -- primary and higher-order. The primary level generates a mental scene with much diverse information for the purpose of directing present or near-term behaviour. It includes perceptual categorization, but no sense of self or use of language. Other animals have it, too. Higher-consciousness is built atop the primary level, includes a sense of self, awareness of a past and future, and language capability. It is supported by the evolutionary newer structures of the brain.
It gets pretty technical at times. There is quite a bit about the brain and neural processes. Information theory is introduced. An earlier book, The Remembered Present, might be a better introduction to his work. In any case, A Universe of Consciousness is founded on his previous works, but adds a lot more. It is a mighty blend of a firm empirical ground and a highly integrated and coherent theory.