In the last decade or so, early-modern “Iberian science” has come to occupy a highly visible position in the research agendas of the international history of science community, along with renewals of long-standing traditions of scholarship carried on by Spanish and Portuguese scholars. This surge of interest in the processes of production of natural knowledge in early-modern Spain and Portugal constitutes an attempt to go beyond the “Black Legend” of Iberian backwardness, religious fanaticism and intellectual conservatism, and much has been done to properly situate the region's scientific output in relation to its actual historical horizons and larger-scale trends. Presently, the 16th and 18th centuries command most attention, the former because of the context of the maritime discoveries and the zenith of Iberian political power, the latter because of what are perceived as conscious projects of reform and modernization carried out by regional elites. The 17th century still remains, however, much prone to be explained in the idiom of decline and its usual narratives. In this paper we address the question of how the systematic study of scientific books printed in the region during the century, which we are presently undertaking, may contribute to a better understanding of the processes, actors and institutions involved in the making of natural knowledge. Although there are some bibliographical repertoires and databases, there still lacks a systematic survey of this output, going beyond mere listings. We delineate the challenges of building a historically sound typology of such material, one that incorporates locally recognized “trees of knowledge” and library-classification schemes. We then argue that, although classifying (and quantifying) the printed sources may help one to gauge the decline thesis, through comparative analyses (internal and external, as well as synchronic and diachronic), proper historical understanding of Iberian science in the period demands several additional steps, that must be incorporated in such a systematic undertaking: As a minimum, one has to map trends and shifts in printers and printing centers, authors' interests and institutional backgrounds, and patronage dynamics (through prefaces and dedications). The construction of proper time-frames and benchmarks for the establishment of such trends is finally discussed, as well as a last, crucial question: the incorporation of readers and networks of circulation into the analysis.