The official textbook for CS 205A is Scientific Computing, by Heath. A great reference on numerical linear algebra for mathematically inclined students is Matrix Computations, by Golub and Van Loan. A classic reference on the conjugate gradient algorithm, thankfully available for free online, is "An Introduction to the Conjugate Gradient Method Without the Agonizing Pain," by Shewchuk.
A set of course notes specific to CS 205A is under construction by the instructor. While he is making every effort to complete the notes as the quarter proceeds, students in CS 205A are still responsible for having the official text on hand! Links to individual chapters as well as the entire set of notes are included below, with a rough status describing how complete they are: