Mine, Mine, Mine! is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

When this enchantment enters, each player puts their library into their hand. Players have no maximum hand size and don't lose the game for drawing from an empty library. Each player can't cast more than one spell each turn. When this enchantment leaves the battlefield, each player shuffles their hand and graveyard into their library.