Introduction: Textbooks are essential component of the educational system that were heavily utilized by teachers and learners. Basic Science textbook authors should review the language structure and terminologies to enhance the readability of Basic Science textbooks. Purpose:The study aimed at analyzing the adequacy in the readability level of the recommended Basic Science textbooks in use junior secondary schools Enugu State, Nigeria. Methodology:An evaluation research design was adopted for this study. The population consisted of all the 60 recommended Basic Science that were approved for teaching of Basic Science in Junior Secondary Schools in Enugu state, Nigeria. The sample size of this study comprised of 33 recommended Basic Science textbook. Purposive sampling technique was used to draw eleven (11) recommended Basic Science textbooks each from JSS1, JSS 2 and JSS 3. The readability of the textbook was determined using Flesch-Kincaid Readability Formula. The researchers subjected the instrument to content validation by three experts, with internal consistency reliability estimate of 0.92. Microsoft office word 2010 was used to assess the readability. The mean of the readability scores for each Basic science textbooks was determined and interpreted using the Flesh's interpretation readability scores relative to Nigerian schools. Results: The findings of this study revealed that almost all the Basic Science textbooks are adequate and can easily be understood by the students. Recommendations: The researchers recommended that the recommendation of Basic Science textbooks should not be based on the reputation of the publishers and the lobbying abilities but should be based on more objective criteria that relate to the textbook quality with the students as the principal focus.