Crisfield's first and second books are excellent sources for anyone from different disiplines. His success can be attributed to explaining the materials in their simple forms and to his notations that is easy to follow. Starting from 1D nonlinear truss elements to 3D beam-column elements, all concepts are explained in a similar way so once you are into it, it is easy to follow the text. I mostly studied his work on finite rotations, and arc-length algorithms.