PopCo by Scarlett Thomas
Alice Butler has been receiving some odd messages - all anonymous, all written in code. Are they from someone at PopCo, the profit-hungry corporation she works for? Or from Alice's long lost father? Or has someone else been on her trail? The solution, she is sure, will involve the code-breaking skills she learned from her grandparents and the key she's been wearing round her neck since she was ten. PopCo is a grown-up adventure of family secrets, puzzles, big business and the power of numbers.