level = std::max(1, level);

    int choice = random_choose_weighted(
                               55, 0, // fixed themed
                               24, 1, // leave alone
             level == -1 ? 0 : 12, 2, // fixed level
        agent == GOD_XOM ? 0 :  6, 3, // manual (too useful for Xom)
                                0);

    int choice_weights[4] = {
                               55, // fixed themed
                               24, // leave alone
             level == -1 ? 0 : 12, // fixed level
        agent == GOD_XOM ? 0 :  6, // manual (too useful for Xom)
        };
    int choice = choose_random_weighted(choice_weights, choice_weights + 4);

        int total_weights = 0;

            total_weights += w;

        // Are we too skilled to get any manuals?
        if (total_weights == 0)
        {
            _do_book_acquirement(book, agent);
            return;
        }