Based on the analysis of the domestic and foreign authors' works, the article proposes substantiation of the educational texts' selection principles for the critical thinking development. The authors use a broad interpretation of the "educational text" concept, considering it as a set of materials included in the educational process with a specific pedagogical goal. The novel Harry Potter and the Methods of Rational Thinking by Eliezer Yudkowski is cited as an example of a non-formal educational text.