A:I’d like to join the library. We’re new to the district you see.
B:Certainly. Well all we need is some sort of identification with your name and address on it.
A:Oh dear. We just moved, you see, and everything has my old address.
B:A driving licence, perhaps?
A:No, I don’t drive.
B:What about your bank book?
A:That’s just the same. Oh dear, and I did want to get some books out this weekend. We’re going on holiday to relax after the move, you see, and I wanted to take something with me to read.
B:Well, I’m sorry, but we can’t possibly issue tickets without some form of identification. What about your passport?
A:What? Oh yes, how silly of me. I’ve just got a new one and it does have our new address. I’ve just been to book our tickets so I have it on me. Just a minute. Here you are.
I’ve just been to book,这里的have been后面为什么直接跟动词不定式to book?