"I think I can safely say that nobody understands quantum mechanics." #Richard Feynman# Basing his discussion on a small number of conceptually simple models (the two-level atom, the two-slit interferometer), the author addresses a number of conceptually interesting questions concerning the puzzles of quantum mechanics. Though the phenomena arising from quantum interference are central, he maintains that they are not the only mystery in quantum mechanics: the deep connection between spin and the statistics of identical particles, the "ghostly" long-range effects that correlated particles exert on each other, and the perplexing role of topology in the interactions of charged particles and electromagnetic fields, are all conundrums yet to be understood.