I would like to recommend "Elasticity: Theory, Applications, and Numerics" by Prof. Martin H. Sadd as a reference for ES240. The book, as its name indicated, is mainly focused on elasticity theory and its applications, but also discusses numerical methods such as finite element method and boundary element method.

Prof. Martin H. Sadd, organized the book into two parts: I. foundations, and II Advanced topics. In part I, the book clearly outlines the basic equations of elasticity, i.e. strain/displacement relation, Hooke's law, and equilibrium equation. The other context of part I is devoted to the formulation and solution of two-dimensional problems. This structure matches the progress of our class very well.

The second part of the book begins with the discussion of anisotropic elasticity, thermo-elasticity, and micromechanics. These topics are complementary to the notes of ES240, and helpful in solving homework problems. In its last chapter, the book introduced finite element method and boundary element method.

One of the features is the book's appendix, in which most of the basic equations and analytical solutions (if possible) in Cartesian, Cylindrical, and Spherical Coordinates are listed. I used it as a handbook when working on assignments.

In Amazon.com, the book is commented as "a welcome addition to the set of textbooks available to beginning graduate students and advanced undergraduates in mechanical engineering" by Biswajit Banerjee - Department of Mechanical Engineering, University of Utah.