I'm using a lot of linear solvers and preconditioners, but mostly, they are magical black boxes to me. Since I'll also have to implement some of them in future, I would like to learn a bit more, exactly how they work an which one is "good" for what.
Since I'm quite fit in the basics (linear algebra, numerics), I do not need a book that covers the full theory. I'm more looking for an extensive, well-understandable description of the various algorithms. Something like a "cook book".