This study investigates the integration of a digital annotation tool (DAT) into an advanced English as a foreign language reading course. Informed by the recent research, the goals of the study are to exhibit the nature of L2 learners' engagement in digital social reading practices and illustrate the linguistic benefits of such practices for L2 learning from a learner perspective. In response to these objectives, a mixed-method research was employed. The analysis of the data including digital annotations and learners' reflection journals reveal that learners' engagement within collaborative reading environments is linked to factors such as the quality of posts rather than the quantity. In terms of perceived linguistic gains, the findings indicate that digital collaborative reading enabled learners to achieve a perceived development in reading, writing, and vocabulary. The study concludes by suggesting further research to examine the use of DAT in L2 teaching and learning settings, which highlight the extent of factors influencing L2 learners' engagement in digital social reading practices.