[Elizabeth blinks at the question, tries to hold in a grin and fails. 'Alien books'. Books about 'aliens'. In general. She knows more or less what he's asking for, but she's going to poke a little fun at the question anyway.]

Oh yes, I have plenty of books about humans in general-- ones from Earth, from Barrayar, from Sokovia... [She waits for the reaction before relenting.] You'll have to be a bit more specific when you use the term 'alien' now. There are plenty of people-- beings-- here who are vastly different from you, but can't be listed under the same category as another group given they share almost no similar characteristics and yet... you might still call both 'aliens'.