This study explores the development of English textbooks in North Korea through corpus-based analysis aimed at illuminating the differences between materials produced during the Kim Jong-il and Kim Jong-un regimes. In the context of educational reforms and changing political ideology, this study investigates BNC/COCA-based lexical coverage and the key lexical features of North Korean middle school English textbooks, highlighting the complexity, vocabulary, and readability of the learning materials. The findings revealed that the Kim Jong-un regime had implemented reforms to improve English language education, with increased lexical diversity, textual complexity, and vocabulary exposure. Although no significant differences were found between the two regimes regarding the lexical coverage of textbooks, the Kim Jong-un regime's textbooks exhibited improvements in diversity, readability, and complexity. This study contributes to a broader understanding of the interplay between political ideology and English language education in North Korea, offering insights that have implications beyond the North Korean context and encouraging reflection on the nation-driven educational reform.