Conceptualizing Individual Differences in Reading delves into the multifaceted nature of reading research through the lens of learner variability. Featuring cutting-edge studies, it explores how cognitive, linguistic, affective, and sociocultural factors, such as metacognitive knowledge, vocabulary depth, working memory, and socioeconomic status, shape reading development in diverse foreign language contexts. From longitudinal analyses of young learners to meta-analyses of reading strategies, the contributions highlight methodological innovation and interdisciplinary insights. By bridging universalist perspectives with individualized approaches, this collection advances theoretical models and offers practical implications for educators, emphasizing the dynamic interplay between individual differences and reading proficiency.