Reading research in K-12 English-speaking contexts reveals that inferential and expository texts cause substantial difficulty for students but less such research exists regarding other languages. It was the purpose of this quantitative cloze-based study to expose any relationship between student difficulty and particular features of the Arabic used in a mandatory Saudi Year 10 Physics textbook. Findings reveal that: (a) These 360 female students appear to be having significant difficulty understanding their textbook. (b) Nouns seem to cause the greatest difficulty, followed by technical- and semi-technical words; adjectives and grammatical particles. (c) Prior knowledge did not appear to reduce reading difficulties. This textbook may present difficulties for such students that go beyond the obvious issues of technicality in Physics text. This is significant because it suggests that the broader language difficulties that seem to characterise science text in English may also be emerging in specialist Arabic.