This descriptive study assessed the linguistic complexity of the three Ghana Senior High School Integrated Science textbooks, using readability index analyses. Simple random sampling was used to select five units from each textbook for testing. Criterion-based sampling was used to select, from each sampled unit, a block of texts of no less than 300 words for analyses. Readability score for each sampled text was generated by feeding the sample into the online readability calculator. Simple descriptive statistics were run in order to organize and summarize characteristics of the sampled text. Then, Analysis of Variance procedures, both parametric and non-parametric, were run to test the statistical significance of differences, if any, among the readability scores of the textbooks. The study established that while science textbooks for SHS 2 and 3 and were suitable for their intended audiences, the readability of Book 1 placed it at the level of university students, and therefore, too difficult for its intended audience. There were no statistically significant differences in the mean readability levels of the textbooks at 0.05 alpha level, suggesting that there is no progression in reading and comprehension difficulty among the three textbooks. A recommendation is made for further evaluation of all the textbooks and particularly of Book 1 for possible revision, which may help students to achieve the intended meaningful learning.