Canonical coherence occurs when subject matter in school is organized to align with the logical structures of an academic discipline. Even though it is highly desired, this condition is an assumption that must be empirically tested, which was the rationale behind our examination of the coherence of topics from middle-school (grades 7-9) integrated science textbooks from Taiwan and Korea. We wanted to determine if textbooks here were able to present science in a way that made it conceptually easier for students to learn and the means whereby coherence was achieved. Based on a list of "standard" science topics from Third International Mathematics and Science Study (TIMSS) research, our comparative study found that while the number of science topics varied by grades and region, their total numbers did not differ significantly. Both regions also focused strongly on physical science topics based on textbook page coverage even as different topics were emphasized (or not). In Taiwanese textbooks, topics were strongly grouped by disciplines in each middle-school grade (a specialist approach) whereas topics from the three main science disciplines were dispersed within each middle-school grade over an academic year in Korea (a generalist approach). Coherence of topics in both regions was found to be supported through a mix of desirable upper triangular patterns within the main science disciplines as well as buttress topics that develop disciplinary ideas over time. The results from our study can create greater awareness of the significance as well as challenges of achieving canonical coherence of topics in science textbooks, especially with respect to integrated science subjects that are extremely common worldwide.