Hmmm... I would hope that a book is in a language I know. American English is what I know best, with some bits of British English from various stories I have read.
I wouldn't mind finding some in languages I am attempting to learn. At present, that is just Japanese I am attempting. I am not very good at it.
I would like to learn Comanche. I have found a source of learning materials. Some of my ancestors are Comanche.