The purpose of this research was to elucidate a continuum of postsecondary text difficulty and to use it to quantify gaps between the text difficulty of high school textbooks and various reading materials likely to be encountered in the most widely chosen postsecondary domains of endeavor--the university, the workplace, the military and citizenship in general. Wide-ranging samples of texts were identified to represent the typical texts found in each domain of endeavor. Using The Lexile Framework [R] for Reading, each text was analyzed to produce a Lexile measure of text difficulty. The resulting 1730 text measures were statistically analyzed and summarized to show the differences in distributions of text difficulty across the identified domains of postsecondary endeavor. The results indicate a systematic continuum of increasing text demand that extends from high school texts to university texts. Furthermore, there were statistically significant increases in text demand from high school texts to citizenship materials, workplace materials, community college texts and university texts. Whether a student aspires to postsecondary education, a job, the military, or just to be an informed citizen, the reading ability required is likely to be higher than what is typically required in high school based on texts that are widely used in this country. This finding is consistent with much of the extant literature about readiness for postsecondary endeavors. However it is dramatically distinct from that literature in applying a more unified theoretical framework and in producing results that are comparable across the investigated domains. It gives new insight to possible methods to address student readiness. For example, if the gap in student readiness is really a gap in text difficulty rather than a result of student failure to learn what has been taught in high school, then any policy solution should address the text gap instead of providing (remedial) "solutions" for a perceived gap in student ability. Furthermore, because reading ability is generally measured with many different scales it currently is not possible to investigate a performance gap with the definitive results observed in this study for text difficulty. Therefore, this paper also calls for a more systematic effort to identify and quantify the reading ability gap in terms of a metric for both ability and textual difficulty. The advantage would be more meaningful measurement of reading ability and findings that are more conducive to instructional and policy actions. (Contains 2 tables and 1 figure.)