Databases For controversial topics, the databases Opposing Viewpoints (password empirelink) and ABC-CLIO Controversies (password solvayhs) will be your best friends. Both of these databases have extensive information about many controversial topics, and their goal is to present all viewpoints so that you can get a well-balanced sense of the facts about an issue.
Books Books can be excellent sources when you are researching controversies. However, pay attention to the type of book you select. There are reference books which are designed to help students understand a topic, which are generally relatively unbiased. If you choose a book that was published for the general public though, it may be trying to convince you of something. That is not a bad thing - you can still use a biased book for facts, as long as you recognize the bias and fact-check the information with other sources.