In recent years, premodern astrology has become a significant topic for scholars. Studies that are now classics, as well as more recent contributions, have addressed astrology and astronomy (the distinction between the two disciplines was not as pronounced as it is today), as well as the perception and reception of these disciplines throughout medieval and early modern Europe by intellectual and political elites and the general public. In all these scholarly works, astrology typically intersects with the construction of secular and ecclesiastical authority and its exploitation for political ends.

Darin Hayton, a historian of science, shows how the traditional approach of writing political history, which eschewed astrological sources, neglected a vital and still largely unstudied corpus of sources that offers a much clearer understanding of how power was conceptualized and enforced in premodern Europe. Where Hayton's work differs from earlier studies, however, and where it makes a welcome contribution to the discipline, is its innovative argument that the Holy Roman Emperor Maximilian I stood apart from his fellow astrologically-inclined predecessors and social peers because of his own significant skills in the art and science of the stars. Astrology was omnipresent throughout the emperor's life. From the moment of his birth until his death, Maximilian surrounded himself with astrologers and was awash in sidereal subjects. For Maximilian, astrology and astronomy were more than vital tools for understanding the wider world and his place within it, although they certainly functioned in that capacity.

Crucially and more practically, these disciplines were, under Maximilian's direct patronage, tools for political self-fashioning. They could be used as a form of propaganda that Maximilian manipulated more fully than any other premodern European authority. Furthermore, he did not just use the elite and traditional sources of poetry and art to spread his astrological messages: aided by the technology of the printing press, which made it possible to publish relatively inexpensive astrological writings and diffuse them extensively around his imperial domains, he subtly used ephemeral texts to disperse his message to a wider audience. These documents included astrological pamphlets, almanacs, and broadsheets, as well as paper instruments designed to teach the prospective university-trained astrologer the complex mechanics of the discipline.

In addition to analyzing elegantly a broad range of primary sources, Hayton also demonstrates command of the secondary English- and German-language scholarship about Maximilian, the Habsburg court, and the emperor's political and cultural legacies. It is well known that the seigneur or sovereign who wanted to demonstrate authority not only ensured that the best minds of his or her generation resided at court, but also patronized them handsomely—and in this regard, Maximilian was no different. In order to consolidate power and inculcate loyalty among his imperial subjects, Maximilian recognized the need to surround himself with university-trained astrologers, whom he considered crucial for the legitimization of his authority. During his tenure as Holy Roman Emperor, Maximilian lavished privileges and resources upon the University of Vienna and its astrological faculty. For Maximilian, the university was a direct conduit of advisers for the imperial court, providing him with astrologers to advance his imperial agenda. In fact, Maximilian's actions helped make Vienna the premier center for studying astrology and astronomy in the sixteenth century. Three Habsburg court astrologers in particular, Johannes Stabius, Georg Tannstetter, and Andreas Perlach, whose writings were directed to elite and popular readers alike, were central to this imperial initiative, and Hayton spends most of his book unpacking and analyzing these men's writings and their impact on an increasingly literate society. The legacy of Maximilian's use of astrology as a form of princely self-fashioning continued under his successor, Ferdinand III, who maintained the practice of ensuring that astrologers held prime positions and responsibilities at the Habsburg court.

Hayton's style is lucid, engaging, and often witty, making The Crown and the Cosmos a pleasure to read. Thirty-two black and white images complement the text, and Hayton analyzes these with grace and skill. He teases out the hidden meanings of complex sources and analyzes how anonymous, early modern readers engaged with these astrological materials, clarifying with their own marginal notes the Habsburg court astrologers' positions and terminologies and even correcting their calculations. Hayton proves that, in the early modern world, imperially-supported and –sanctioned astrological writings were successful in advancing the imperial agenda of inculcating loyalty and support for the person of the emperor himself, especially at a time when an ascendant Ottoman Turkish power was threatening Vienna and other imperial dominions. With his elegant and erudite study, Hayton offers a stellar contribution to the growing literature on astrology and its significance for understanding premodern politics. This wonderful book will undoubtedly be a cornerstone work on the topic for years to come.