In Memoriam:<br>Steven Weinberg (May 3, 1933 – July 23, 2021).<br><br>This is a sad occasion, writing this book review one week after the passing of physicist Steven Weinberg. Having been a lifelong student and admirer of Weinberg, there was no way I was going to ignore his book of lectures on astrophysics. It is dense. It is terse. It is challenging. However, Weinberg does not promise anything that he can not deliver. As is his custom, Weinberg stresses the interplay between theory and experiment, how to arrive at numbers. Interestingly, dimensional analysis is used in various circumstances (pages 42-49). You get a derivation of relativistic equilibrium condition (page 68, also, you are referred to his 1972 tome on General Relativity for alternative derivation). Tools of the trade include the oft-utilized method of "integration-by-parts" and the oft-utilized "power series expansion."  I enjoy section #2.1: "how observations are used to find the properties of binary stars." (page 83). You derive inequalities (examples: tidal distortion, page 87, maximum luminosity, page 149 and Schwarz inequality, page 190).<br>You will get a review of gravitational radiation in preparation for a discussion of LIGO (pages 98-104).<br>There is a discussion of HII regions (ionized Hydrogen surrounding stars): it is insightful, lucid and easy to follow (see section #3.2). You will learn something new as you consider effects of viscosity in gas rotating around an axis of symmetry (pages 150-153). A discussion of Galaxies concludes the lectures, recall the Boltzmann equation and Euler equations of hydrodynamics, while learning that "the formalism presented above allows the construction of equilibrium distribution functions for galaxies in clusters and for dark matter." (page 178). A motivation to peruse this book, according to Weinberg, is the opportunity to bring his earlier book up-to-date (1972, Gravitation and Cosmology). Because my personal library holds many of Steven Weinberg's bibliographic references, the lectures were easier to assimilate than they might otherwise have been. There is more here to learn and I intend to learn it: if for no other reason than to pay homage to a brilliant physicist, a fine teacher and a fine human being.<br>He will surely be missed.