Pronunciation

Everyone knows the stories about how wrong you can get what you are trying to say in Chinese if you are not careful with your pronunciation. Most of the time, I've had no problems with it but as I was trying to organise some boxes to be sent here from Kunming when I was moving, I had a little trouble trying to make the (already annoyed) lady understand me. The problem was that both 'tree' and 'book' are pronounced with the same sound ('shu'), just the tone is different. It went something like this:

"I'd like to send some boxes to Chongqing by train."
"Ok, what's in the boxes."
"Just kitchen stuff and some books."
"What?!?! How many trees??"
"Oh I don't know, it's one box."
"But how can you fit even one tree in a box?!?"
"What...? No, not trees! Books!"
"Huh?? But even one tree is so big!! How can you send them on the train?!?"
"Nooooo, the kind of books you can read."
".....I see. Books. Whatever. [...foreigners...dried pig ears for brains, they've got]"