Bitcoin is actually much more like a commodity than a stock, and should be considered an extremely high risk investment. It is still an experimental technology, the likes of which have never been seen before in history of human civilisation, and has the potential to completely revolutionise global trade. Historically, investments in such technologies have either made their investors rich beyond their wildest dreams when it proves to be a runaway success, or sent its investors broke when the whole thing failed completely. Since nobody knows whether Bitcoin will succeed or fail, you definitely should not invest more than you can afford to lose.
Remember, past performance does not guarantee future results.
As for mining, you should always remember that it is not "free money" or a get-rich-quick scheme, it is a vital service to the Bitcoin network (without which Bitcoin couldn't survive), and miners get paid for providing this service. Nothing more. It is a highly competitive industry, and you need to really know what you're doing if you hope to make a profit from it.
