The purpose of Ligand Efficiency Indices for Drug Discovery: Towards an Atlas-Guided Paradigm is to introduce in a concise and self-contained form the concepts, ideas, applications and examples of efficiency-driven drug discovery to the biomedical community at large. The book emphasizes the use of 'new variables' and more objective numerical methods to drive drug discovery in an encompassing way. These 'new variables' are based on Ligand Efficiency Indices (LEIs) formulated in a way that permits mapping Chemico-Biological Space (CBS) in an Atlas-like representation. It provides a practical and timely discussion of the concepts, ideas, applications and examples of efficiency-driven drug discovery. This book emphasizes the use of a graphical representation and objective numerical methods to drive drug discovery more effectively. It presents the definition of LEIs and the corresponding efficiency planes within an atlas-like environment to provide a robust graphical and numerical framework for medicinal chemists and drug-discoverers.