<![CDATA[This study aims to develop and evaluate an interactive Microeconomics textbook based on Project-Based Learning (PjBL) to support students’ higher-order thinking skills (HOTS) and learning outcomes. The study employed a Research and Development (R&D) approach using the ADDIE model and involved 35 undergraduate students enrolled in the Economics Education program at Universitas Musamus. Data were collected through expert validation, lecturer and student response questionnaires, and pretest and posttest assessments. The data were analyzed using descriptive statistics, the Shapiro–Wilk test, paired-samples t-test, and N-gain analysis. The needs analysis indicated that the existing learning outcomes were predominantly focused on lower-order cognitive levels, with 66.7% at C2, 16.7% at C3, and 16.7% at C4, while C5 and C6 were not explicitly addressed. Expert validation yielded an overall score of 93.1%, while student and lecturer responses reached 92.9% and 94.3%, respectively, indicating high levels of validity and practicality. The paired-samples t-test revealed a statistically significant difference between the pretest and posttest scores, t(34) = −16.77, p < .001, with a mean N-gain score of 0.57, categorized as moderate. These findings indicate that the developed textbook is valid and practical and has the potential to support improved learning outcomes and HOTS-oriented Microeconomics learning. However, the use of a one-group pretest–posttest design without a control group limits the extent to which improvements can be causally attributed to the developed textbook.]]>
