The work describes, with a simple style and devoid of mathematical formalisms, but with frequent references to numerical data, the state of the art of the research of stellar astronomy. Published in Italian in 1877, it was a fairly international success: it was translated into German (Die Sterne, 1878) and in French (Les étoiles, three editions: 1879, 1880 and 1895). After a first chapter on “The general aspect of the sky”, the second, entitled “Stellar Physics”, is dedicated in large part to the spectroscopy studies, a discipline to which Secchi gave a remarkable and original contribution. It is therefore no coincidence that this chapter is by far the most extensive. The author provides ample historical notes on the development of instrumentation, which mostly refer to its activities in the Observatory of the Roman College; It presents the main result of his catalogation work, that is “all the stellar spectra […] Can be traced back to 4 main types (p. 83) “; he compares the stellar studies with those made about the sun, already widely treated in Le Soleil. In the third chapter on “Stellar movements” are described, among other things, the first attempts to measure the radial velocity of a body from its spectrum thanks to the Doppler effect. The fourth chapter, “Vastness of the starry space”, deals mainly with the determination of distances in astronomy; While the fifth, “Structure of the Universe”, is devoted to studies on the distribution of stars and nebulae in space. The concluding chapter, “Ideas about the greatness and structure of the Universe”, summarizes the main results for points and offers interesting considerations of the author, such as the conviction that the observed diversity in the creation implies that “life fills the Universe, and Life must be associated with intelligence “(p. 339). The work is complemented by some records of fundamental, variable, coloured, double stars and notable objects. The image depicted here represents the frontispiece of the opera with the panel at the front, which illustrates some binary systems of coloured stars.