I just got my delivery from Amazon: "Linear Algebra" (George Shilov) and "Metaprogramming Ruby" (Paolo Perrotta).

I have a degree in Physics but I find my linear algebra to be a little rusty so I bought Shilov's book to brush up. I bought Perrotta's book because while reading over some of the Rails 3 codebase, too often I find bits of code that I don't quite understand, at least without some effort.