This is a book review of Multiverse Theories: A Philosophical Perspective by Simon Friederich. Cambridge University Press, 2021. Pp. 214, 25 × 17.5 cm. Price £49.99 (hardbound, ISBN 978 1 108 48712 2). Few topics in cosmology are as hotly debated as the Multiverse: for some it is untestable and hence unscientific; for others it is unavoidable and a natural extension of previous science. There are well known and respected cosmologists on both sides of the debate. Can this book by philosopher of science Simon Friederich offer anything new? Yes. At the beginning of the last chapter, he states explicitly what the reader who has come that far will have noticed: "Throughout the discussion of multiverse theories in this book, I have set asided the most heated discussions about the multiverse and ignored the most scathing criticism of such theories ...." Also interesting is the fact that "[t]he considerations on multiverse theories in this book are somewhat unusual ... for they have been developed and compiled by someone who has never had any strong feelings about their central topic ...." The result is an interesting book which is not only about the Multiverse but also about the epistemology of the Multiverse. Tegmark had defined for `levels' of Multiverses: the Level I Multiverse is what many call the Universe (his Universe being what many call the observable universe). The Level II Multiverse consists of other universes (or Tegmark's Level I multiverses), perhaps with different values of the constants of nature, different laws of physics, or different initial conditions. The Level III Multiverse are the many worlds in Everett's interpretation of quantum mechanics; and the Level IV Multiverse is Tegmark's own Multiverse of mathematical structures. Level I is accepted by essentially everyone, Levels II and III by many, while Level IV is speculative. The bulk of the book is concerned with the Level II Multiverse (which is usually meant if it is not specified in detail), though the penultimate chapter discusses, and rejects as incoherent, Levels III and IV and also David Lewis's "Multiverse" of modal realism. Much of the discussion of the Multiverse is in the philosophy rather than the physics literature and thus might present something of a barrier to physicists interested in the epistemology of the Multiverse. Friederich's book is a good bridge across that gap and otherwise a good introduction to the topic. I recommend it highly.