The best investment option involving Bitcoin is.... Bitcoin itself. Bitcoin was originally intended to be a currency. But nowadays, it is mostly behaving as an investment asset. And I would advice every one to stay out of the other Bitcoin-linked investment options, such as crypto-stocks. Most of these schemes are ponzis, run by conmen.
Well, investment in bitcoin indeed very good, but you'd better wait for the right time to buy a bitcoin, because if not, it will count against their own investments, so maybe you have to wait for the price to be low. besides, altcoin also be a good option for investment, because so many altcoin new, promising, like ETC
currently altcoin is a good investment, the potential benefit is greater than the investment in bitcoin or other investments.
but you should still be careful when choosing altcoin, because there are some altcoin also ended with the scam.