This thesis describes the design, development, and evaluation of a social digital library to support users in finding information from a user-based point of view. This particular research project has been motivated by the fact that there has been very little research on the social features in digital library interfaces. This research aims to design a novel digital library interface by applying the concepts of social features to digital libraries. Also, the thesis investigates whether the functionalities in the social digital library help participants to accomplish different task types with minimum effort. Social features here refers to clustering users' interacting in a virtual community along with social information such as reviews, the number of recommendations and items/ viewed items by other people. In order to gain an insight into the social features that are useful for users to compt~te search tasks, I began with the development of The Victorian Times Digital Library by using PHP & MySQL. Initial design interfaces were tested by usability tests in order to overcome usability problems. Based on participants' feedback, the chosen features were presented in the social digital library and represented in different screens. These interfaces were then evaluated by several usability tests using an iterative design approach. Also during an iterative phase of design, the interfaces were revised based on Information Foraging Theory in order to increase strong information scent. The final version of the social digital library was then evaluated against a conventional interface in an effectiveness test. I performed an experimental study to examine the use of features in digital libraries to perform the tasks. A total of twenty four participants were recruited to perform various tasks on both interfaces and to rate their preferences. The outcomes of the effectiveness test were positive, with half of participants (12 out of 24) preferring the social interface and the rest of participants preferring the traditional one. Also, the results showed that the social digital library was able to help participants to accomplish different types of task with minimum time and effort. This was considered as a good result given the quality feedback from the participants. Also, some of findings emphasized the importance of social activities and look and feel over a set of social features.