Extensive reading has been widely implemented and investigated in the learning of English as a foreign language, but the study of genre effects in extensive reading has been rarely touched. While fiction reading is associated with intrinsic motivation, nonfiction deserves inclusion as it is vital for learners’ success in higher education and career. In the present study, a pre- and post-test research design was exploited in a 16-week reading program with 63 junior high school students in Beijing, who were from two intact homogeneous classes reading informational texts (namely, newspapers & magazines, NM) and fictional graded readers (GR) respectively, and their gains in reading, writing ability, and reading attitude were compared. Results show that both groups had gains in reading, writing ability, and reading attitude from pre- to posttest, and Group NM had more gains in reading and writing ability, but only outperformed Group GR significantly in writing improvement. The results are explained by genre, experiment design, and reading style-related factors. Findings of this research suggest the necessity of including informational texts in an extensive reading program for EFL learners, and provide a deeper understanding of the relationship between different degrees of extensive reading and their effects.