The game presents you with a series of word puzzles. As these are answered, more puzzles open up. The barest of plots links these together. I think most will find the bulk of the puzzles are easy--producing synonyms, answering crossword-type clues, decoding anagrams or cryptograms, etc.
Once you answer a certain number of puzzles, you are invited to join a boss battle. Your previous answers will be used to defeat the boss.
I would say the puzzles are largely fair, particularly because you don't need to complete every word puzzle for a successful ending (though, perhaps there is another ending for players that solve every word puzzle). There are two puzzles that I still completely do not understand--but, perhaps someone else will immediately recognize a method to solve them.
For anyone who loves puzzles but also wants at least some narrative for those puzzles, this isn't what you're looking for.
For anyone who loves crosswords, cryptic crosswords, or other word puzzles but does not play IF, this would probably be a fun experience. It may also be a really fun play with a friend or family member, especially the type of couple that will do a crossword together.