This study aims to identify the key factors that influence library users’ satisfaction with the indoor environmental quality (IEQ) in a contemporary university library, focusing on both perceived IEQ and individual user characteristics. Through a thorough literature review, it pinpoints indoor environment quality (IEQ) and individual users characteristics as critical influences of satisfaction. Data were collected from 404 users within four specific study areas of a selected university library. The study employs structural equation modeling (SEM) and generalized ordered logistic regression (GOLRM), to examine the relationships between perceived IEQ factors and user satisfaction. The SEM showed a good fit and highlighted significant impacts of acoustic quality (coefficient = 0.24, p < 0.01) and interior design (coefficient = 0.65, p < 0.001) on satisfaction. GOLRM analysis revealed that factors such as “age” (odds ratio = 0.810, p = 0.039), “feeling” (odds ratio = 1.420, p = 0.017), and “location (6th floor group-based study area)” (odds ratio = 2.844, p = 0.004) significantly enhance satisfaction, though advancing from medium to higher satisfaction levels poses challenges. These insights suggest that customizing library spaces to meet diverse user needs can markedly improve satisfaction. The study underscores the importance of integrating environmental and personal factors in library design and showcases the effectiveness of SEM and GOLRM in exploring complex interactions within built environments. This approach offers a valuable framework for designers and facility managers to align library spaces with user expectations, making a substantial contribution to the field of built environmental design research.