Book reviews are important in offering guidance to prospective readers. What is expected from them is to be not only informative and evaluative but also unbiased and balanced. Therefore, the use of correct discourse is necessary to prevent asymmetrical domination of the reviewer, and to create a healthy setting to sustain credibility of book reviews in terms of prospective readers. In that sense, this study investigated two discourse devices, namely euphemism and dysphemism. Euphemism can be defined as polite and agreeable words or expressions that are used in place of harsh or offensive ones; however this research investigated if these expressions might lead to undue praise for a book. On the other hand dysphemism is a kind of language that uses disparaging and derogatory terms instead of complimentary or neutral ones. Reviewers may consciously or unconsciously use these linguistic devices in their critiques of books, however; the balance between them is of great importance because any unbalanced negative or positive critical act may bring about unfair judgements in would-be readers regarding the quality of the mentioned book. The present study investigated a hundred book reviews and picked up euphemistic and dysphemistic expressions. The result is of importance in helping the book reviewers to choose the true word of expression without being unnecessarily soft or offensive. Any possible biases against a book because of book reviewers' inattentive word selection may be prevented in view of the present study. Finally, this study is important for instructors of academic writing to increase their awareness for the importance of discourse devices in book reviews, which is necessary for sustainable development of education; in other words, instructors of academic writing at universities may rearrange their instruction curriculums through saving a slot for euphemism and dysphemism for prospective students.