Should you invest in the stock market? It depends. What is your risk tolerance like? Where are you in terms of your financial education?
I personally have a Vanguard 500 Index Fund but I do not think that means I am "investing" in the stock market. I say that means I am exposed to the stock market. Any idiot can sock money away in an IRA or index fund. However investing in the stock market (in my opinion) takes more sophistication than just "saving" money in a fund managed by someone else. Really investing requires you to learn how to study the technicals in order to determine the financial health of a company and make an informed decision about whether or not to put your capital at risk there.
Putting your money away in an index fund exposes you to the stock market but offers zero protection against systemic risk. When the the S&P crashes, so does the value of your mutual fund. It's alright for me right now because I need to be getting some kind of yield on my savings to stave off inflation. However, if the S&P falls too much I know when to get out. Paper assets also are not very tax efficient . You can argue that IRAs and 401ks are tax deferred but why defer taxes when with real estate you can basically eliminate them?
I would highly recommend The Intelligent Investor by Benjamin Graham. He was Warren Buffet's mentor and the book is a timeless classic on the stock market and value investing. It was and still is an eye-opening read that I return to periodically. I think there's definitely a lot of money to be made in the stock market but whether or not it's a fit for you depends on your specific financial goals, temperament, and frankly -- intestinal fortitude.