From now until 8pm (UK time) Sunday, Football Manager 2017 will be entirely free to play through Steam. That’s over seventy hours of managerial action (assuming you forgo all sleep, which I wouldn’t necessarily advise) at no cost.
During that period, the game will also be sold at 50% off, making it $25 USD (or regional equivalent). The sale offer extends a little bit past the free weekend, all the way to 8pm (UK time again) on Monday 27 March. Plenty of time to decide whether it’s a keeper.
Any progress you make over the free Football Manager 2017 weekend can be carried over if you end up buying the game.