While you may not be able to figure out the whodunit, you'll have no problem reading Agatha Christie's classic Murder on the Orient Express. The prose is clean and simple, and the novel is broken up into three handy-dandy sections: in Part 1 the facts are sorted out, in Part 2 the evidence is collected and reviewed, and in Part 3 we get Poirot's analysis of the case. Use the novel as your personal casebook; most editions even include a diagram of the train.
However, you might want to take this opportunity to brush up on your geography. Checking out a map will help you track the train's route from Syria to Belgrade and beyond. The novel also includes a smattering of conversational French, so a phrasebook may be just the thing if you're an aspiring sleuth – or if you find yourself hanging on Poirot's every word.