Hearthstone? Good! You can start now. The first wing of the new adventure is available to players today; it'll send you through the Arachnid Quarter in a trip down a spider-filled memory lane. If you're on the fence about trying it out, you can take on this wing for free now through early September (the exact date for the end of free access will be announced later on).
Players will be able to purchase further wings of Naxxramas with either in-game currency or real money, with discounts available for bulk purchases. But you don't have to just hope you'll enjoy the adventure; you can log in and try it for yourself right now.