Get some more food for your test-preparation brain

Here are a few interesting resources you might want to try to sharpen not just the numerical skills, but also the way to think. The Pyramid Principle:Logic in Writing and Thinking is an interesting book that helps in structured thinking and problem solving. Could be quite handy in case interviews.

Then there is the popular How Would You Move Mount Fuji?: Microsoft's Cult of the Puzzle - How the World's Smartest Companies Select the Most Creative Thinkers, which is all about creeative problem solving.

You might also find the Mike Bryon data interpretation book useful