Literature reviews are a particularly useful resource when doing research. They address the issues involved in a specific question and the debates among scholars. They map out the intellectual terrain succinctly and give you the major landmarks in terms of key authors and significant titles for greater understanding.
These kinds of reference books provide overviews that address major issues within a field of study. The authors not only discuss key content but provide a more sophisticated level of analysis and contextualization than you might find in a textbook or introductory study. The authors are chosen for their research areas and deliver authoritative essays. The material they choose to include in their bibliographies are good points of departure.