This is a comprehensive list of reliable websites providing quality Islamic literature as a resource to further your knowledge.
Al-Islam.org - http://www.al-islam.org
Created and maintained by the Ahlul Bayt Digital Islamic Library Project (DILP). Provides online quality Islamic resources, related to the history, law, practice, and society of the Islamic religion and the Muslim people, with particular emphasis on the Twelver Shia Islamic school of thought. It serves as a repository for advancing your knowledge about Islam further and acts as a source of education and enlightenment.