Samarskii A. Numerical Methods for Grid Equations. Vol 2. 1989

Textbook in PDF format

The Mathematical Theory of Iterative Methods.
Two-Level Iterative Methods.
Three-Level Iterative Methods.
Iterative Methods of Variational Type.
Triangular Iterative Methods.
The Alternate-Triangular Method.
The Alternating-Directions Method.
Methods for Solving Equations with Indefinite and Singular Operators.
Iterative Methods for Solving Non-Linear Equations.
Example Solutions of Elliptic Grid Equations.
Methods for Solving Elliptic Equations in Curvilinear Orthogonal Coordinates.
Appendices