This study investigates the effect of the unified theory of acceptance and use of technology (UTAUT) and DeLone and McLean information system success model (IS success model) on facets of system use for digital library systems. These facets include lean measures (e.g. frequency, duration, and intensity) and rich measures of system use (e.g. deep structure use and cognitive absorption use). The study overcomes the general description for some constructs, for instance facilitating conditions and quality, and assesses the effects of sub-constructs on system use facets, such as smart and traditional facilitating conditions. Data was collected through a cross-sectional survey in three universities. Component-based structural equation modeling software was used to analyze the data and assess the research model. The findings indicate that there is variance and consistency in the antecedents that influence the facets of system use. The lean measure was predicted by performance expectancy, traditional facilitating conditions, system quality, and behavioral intention, while the rich measure, particularly deep structure use, was influenced by performance expectancy, effort expectancy, traditional facilitating conditions, system quality, and behavioral intention. Furthermore, cognitive absorption use, a rich measure, was impacted by performance expectancy, service quality, system quality, and intention. This study provides a theoretical contribution and practical implications relevant to academics and practitioners in areas related to digital library systems.