Your books are two pounds...,

[Silverobama]

I was about to send some books to a friend. The weight limit is two pounds, so if the package weighs more than that, you have to pay extra. The staff member told me this after she weighed my books.

Your books are two pounds overweight.

Is my translation natural?

 

[emsr2d2]

I was about to send some books to a friend. The weight limit is two pounds, so if the package weighs more than that, you have to pay extra. The staff member told me this the following after she weighed my books.

Your books are parcel is two pounds overweight.

Is my translation natural?

See above. You could also say "Your parcel is two pounds over the weight limit".

Two things:
1. What do you mean by "The staff member"? You haven't mentioned a business/company/shop up to this point so we have no idea who this person is. You need to preface it with something like "When I took my parcel to the post office, the clerk said ..."
2. How did she know what was in the parcel? Presumably you packaged them up before taking them to the post office so unless she's got X-ray vision, she would have no way of knowing that you were sending books.

 

[5jj]

Your books are two pounds overweight.

Was the parcel two pounds over the limit, or just over the two-pound limit?

 

[Rover_KE]

Are imperial weights and measures customarily used in China rather than metric ones?