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