If you enjoy any sort of word game, you'll enjoy this immensely. If not, it's probably not your cup of tea.
I've had Bookworm on my phone for years, and I'm happy to now have it on my computer as well. However, it is missing some of the features I enjoyed on my phone, such as the themed "books" you unlock and complete by spelling certain words.
The whole point of Bookworm is to utilize both your vocabulary and the letters to spell the longest and most challenging words to score points while preventing flaming tiles from reaching the bottom and turning everything to ash (and thus ending the game). There are green and yellow tiles you can use to earn bonus points when completing a word as well. There's no timer, however, and the flaming tiles only move down every time you complete and submit a word.
The good news is that you can "play" with the tiles to spell what are potentially are words, and if it is a word, the game will accept it (and may define it for you as well, if you're interested in vocabulary building). If it's not a word, the game won't accept it, leaving you free to try another selection. You can also click on our worm friend to scramble the tiles--but be warned, you'll suffer the penalty of newly added burning tiles for the privilege.
Depending on how you want to play, you can make the game as challenging or easy as you want it to be. There's also a second mode in the game, the Action mode, that IS timed in the sense that flaming tiles are far more prominent, forcing you to move faster to prevent the library and tiles from catching fire--if you're up for the challenge.
For $4.99, it's a bargain for any wordsmith or puzzle-lover.