Taking an effective authorial is important for writing persuasively in academic domain. Yet, interpersonal aspects such as stance-taking are, equally, acknowledged to be a challenge, particularly for EFL and novice writers. This study investigates the employment of linguistic resources realizing an authorial perspective in textbooks Prefaces written in two different disciplines : soft and hard. To this end, 40 Prefaces (20 from each) were analyzed within the Engagement framework (Martin and White, 2005). The objective is to explore the main trends and cross-disciplinary variations between the two groups in employing the Engagement resources when they present, argue for, and evaluate the topics of their books. The results have shown a general tendency among authors of both groups to employ far more heteroglossic (Expanding and Contracting) approaches than monoglosses (bare assertions) and therefore the authorial stance seems to be dialogistic and inviting. There is, also, a cross-disciplinary variation in Contracting deployment as it is found more frequent in hard than soft sciences. The findings may bear some pedagogical implications for academic writing instructors, EFL and novice writers.