This is a book review of LONG_Dark Matter and Dark Energy by Brian Clegg. Two introductory chapters describe the main topics (missing matter and the accelerated expansion of the Universe), and give a very brief introduction to the contents of the Universe and how our ideas of the structure of the Cosmos have changed with time; subsequent chapters look at dark matter in more detail, the Big Bang model, accelerated expansion, and ideas about the future of research on those topics. I would like to give the book a better recommendation, since it is generally well written and manages to give a good overview of two rather broad topics. However, numerous small mistakes, though not crucial for the main narrative, prevent me from doing so. On the other hand, Clegg includes some things usually missed in books at this level (or higher).