This paper focuses on the procedure and results for analyzing text-difficulty in lower-secondary chemistry textbooks in the Czech Republic. The authors use established methodology for text-difficulty analysis by Nestler, adapted by Prucha and Pluskal by adding a second independent analyser to improve reliability. Some textbooks do not follow the expected trend of either text-difficulty coherence or increasing text-difficulty between books for the 8th and 9th grade. No trend in topic difficulty was found either. The results show that learning outcomes may differ significantly when different books are used, despite the fact that they are supposed to support the same curriculum. For this reason, the results serve to support not only teachers when selecting a textbook, but also researchers as a starting point for lesson observations.