If you don't want to spend hours playing the games, there's a daily game that can be completed quickly. This is a great way to just pick up your iPad or sit in front of your Mac, play five games and then go do something else. In addition to the daily game, each game includes both classic and timed games in easy, medium and hard difficulties. Your score for the daily game and the regular games is compared against other players through Game Center.
Shuffle: in this game, you're tasked with finding as many words as possible with a limited set of letters. There's a target word that uses all of the letters, and you get to advance to the next puzzle.
Wordsearch: this is the equivalent of those books you see old ladies carrying onto airplanes. There's a grid of letters and a list of words; your goal is to find all of those words in the grid of letters, "circling" them by running a finger over them, within a specific period of time.
Hexxed: this game features a group of hexagonal tiles. You trace your finger through the tiles to make a chain of letters, and you're scored based on the length and complexity of the word. There are special tiles that provide extra points or time, helpful for getting a higher score.
Gridlock: like Hexxed, except you have a crossword-like grid of letters. Once again, you trace through the tiles to make a word of a chain of letters. Once you've cleared all tiles of a certain shade off of the screen, a new set of tiles appears. There are tiles that explode and clear out areas and other tiles that add more time.
Spellmaster: in this game, four words are flashed on the screen, only one of which has the correct spelling. You need to tap or click that word to continue to the next word. Get a lot of correct spellings in a short amount of time, and you're at the top of the results list.
As you get to certain levels in each game, you get "book awards" that show up in a bookcase with your picture. For example, you get the Dracula award for playing a game after 7 PM, Les Miserables for finishing a game of Hexxed without using the wildcard, etc...
The Mac app isn't perfect -- for some reason, every time I paused the app, it crashed -- but the iOS app works very well. If you're a fan of word games and want something to burn time when you're waiting for an appointment or bored on a flight, Astraware Word Games is well worth the money. It's also a fun way to test your word skills every day.