This book entitled Studies on the Spectrum and the Energy of Graphs is a humble attempt at making a small addition to the vast ocean of results on the spectrum and energy of graphs in graph theory. We mention some very significant developments in the theory of eigenvalues and energy of graphs and also some recent results in the spectral theory of graphs. Some parts of the results mentioned in this book have been presented in international conferences and appeared in international scientific journals. The author is happy to share that the chapter on Reciprocal Graphs was presented in the ICM 2006 at Madrid.