to be or not to be rude?

i got onto the bus this morning and sat down next to this guy. i got my book out and got as far as one line down when he started talking to me. he said it was getting colder. politely, i replied. yes. this didn't deter him and he started asking questions. i made my answers short, polite , then looked back at my open book, indicating i didn't really want to talk. but this clearly had no effect. he just kept going. even when i replied things like 'if you say so' ('but i know so!' he said) or 'i'm not really interested in banking' ('well, let me tell you...'), he wouldn't stop. i didn't want to be rude, but on the other hand, i really just wanted to read my book. i wondered whether telling him this would make him stop, but decided it probably wouldn't. but so, what should i have done? short of saying 'i'm sorry but i want to read my book', i mean.