A Comparative Analysis of the Readability of College English Textbook Reading Texts Against CET-4 Standards: A Case Study of New Navigation English and New Future English at Guangzhou College of Commerce

To verify whether the difficulty design of college English textbook reading texts aligns with graded teaching requirements and CET-4 proposition criteria, this study takes 48 reading texts from <italic>New Navigation English</italic> (Book1&amp;2) and <italic>New Future English</italic> (Book1&amp;2) adopted by Guangzhou College of Commerce, with the June 2025 CET-4 reading texts as reference. Using Flesch Reading Ease (FRE) and Flesch-Kincaid Grade Level (FKGL) as core indicators, plus average characters per word and average sentence length as auxiliary metrics, the study measured readability and conducted one-way ANOVA via Microsoft Word and SPSS 27. Results show both textbook series follow progressive difficulty design: <italic>New Navigation English</italic> (Book 1) (the least difficult) is suitable for CET-4 transitional training; <italic>New Future English</italic> (Book 1) (CET-4 equivalent difficulty) serves as basic CET-4 preparation material; the second volumes of both series (above CET-4 difficulty) are for advanced training. Significant differences in readability and average characters per word only exist between <italic>New Navigation English</italic> Book1&amp;2, with no statistical differences among other textbooks. This study provides quantitative references for college English textbook selection, adaptation and reading teaching difficulty design.