I've just released a big pack of solitaires that covers all the popular favorites plus some unique, lesser-known variants. There's a bit of everything in here, each with its own challenges and strategies.
If you're into solitaires, you probably know Spider and Klondike already. But have you tried Mrs. Mop, Sultan or Baroness? I've mostly steered clear of the solitaires that are often unsolvable, and for those that are like that - Scorpion for example - I've added more reasonable variants, that are more fun to play. Overall there are over 70 different variants in the game.
Personally, I'm a big fan of the Spider 4 SUIT variant. I can spend hours using undo and trying to solve a specific deal. :)
The game's in early access right now. There's still some polishing to do here and there. If there's a specific variant of your favorite solitaire that you'd like to see added, just let me know.