import re


def book_number_from_path(book_path: str) -> float:
    """
    Parses the book number from a directory string.

    Novellas will have a floating point value like "1.1" which indicates that it was the first novella
    to be published between book 1 and book 2.

    :param book_path: path of the currently parsed book
    :return: book number
    """
    num = int(re.findall(r'[0-9]{2}', book_path)[-1])
    return num / 10