Although Rhiannon's Realm is very much a mah jong solitaire-style game, the developers have gone to some lengths to make it a deeper, more interesting experience.
 
The games is themed around Celtic runes and a story of an evil sorceror who has locked away the secret of the seasons. As you complete levels, you go further through the lunar cycle and progress toward undoing the spell. You can also play in quest mode or in single games with the layout and background of your choice. Game play is equivalent to tile solitaire games, but if you run out of matches, the game will let you shuffle the remaining tiles without resetting the board!
 
The artwork and wallpaper that accompany the game are quite stunning. So for your $20, you get a fun game, with lot of levels, and some very nice backgrounds.