Feynman Lectures on Computation
The book starts off by examining at the basics of computers such as logic gates and how to make them from transistors. This is followed by chapters on the theory of computation - Turing machines and the like - and on information theory. Feynman then looks at issues related to the thermodynamics of computation. The next chapter is on quantum mechanical computers, but its interesting to note that the idea here is to do classical computation on the scale of atoms, rather than to get exponential speedup. The last chapter examines the physics of actual computers, in particular VLSI technology.