Quantum theory is one of the most important and successful theories of modern physical science. A fact all the more remarkable because quatum theory is a theory that few understand. Most academic textbooks on the subject are written for specialists, filled with complex jargon and dense mathematics. In contrast there are many popular presentations of the inherent 'weirdness' of the quantum world that are light on jargon and contain no mathematics.Together these presentationsserve to create the impression that there are two theories - the 'serious, one and the 'wierd' one. Baggott successfully bridges the gulf between these presentations by grounding the discussion of the theory's profound problems directly in its mathematical formalism in a way that under-graduatestudents and interested individuals can follow.