'Get data for name. By default returns data for all book_ids, pass
in a list of book ids if you only want some data. Returns a map of
book_id to values. If a particular value could not be decoded, uses
default for it.'

@read_api
def get_custom_book_data(self, name, book_ids=(), default=None):

    return self.backend.get_custom_book_data(name, book_ids, default)
