Mathy LWers will probably love Scott Aaronson's Quantum Computing Since Democritus, which is funny, insightful, cutting-edge, and just as LW-ish as Gary Drescher's Good and Real.

In addition to lots of stuff on quantum mechanics, quantum computing, theory of computation, computational complexity, cryptography, and cosmology, it also includes:

• A steel-manning and then rebuttal of Penrose on AI.
• A discussion of free will and Newcomb's problem
• A discussion of anthropics (Bostrom's SIA vs. SSA) and the doomsday argument

It's based on his 2006 lecture notes but has been updated in response to new discoveries, and one section of the preface explains all the new stuff that has happened that required revising the manuscript (e.g. fully homomorphic encryption, and Chiribella et al.'s proof that quantum mechanics is the only set of rules consistent with some general axioms of probability theory and one additional axiom.