def radicalreads(soup):
    """
    Get book titles from a radical reads page.
    """
    content = soup.find(lambda x: x.name == 'div' and x.get(
        'class') == ['entry-content'])
    tags = content.find_all(
        lambda x: x.name == 'a' and 'https://www.amazon' in x.get('href', ''))
    titles = set(map(lambda x: x.text.strip(), tags))
    return titles