Scrabble Blast Deluxe has very little to do with actual Scrabble, except that the tiles are modeled after those in the classic board game and that points in the game are allotted based on the value of the letters you use. But unlike in traditional Scrabble, instead of playing letters out of your hand onto a board, the objective in Scrabble Blast Deluxe is to create words out of adjacent tiles to make them disappear. As you use letters, additional ones fill in from above, until you've used the given 100 letters. This particular detail isn't true to Scrabble, and it's not unlikely that you'll come across repeats of letters (such as Q) that wouldn't be found in a normal Scrabble bag.
The gameplay is similar to a few other games like Bookworm and Bespelled, but Scrabble Blast Deluxe isn't quite as polished as its PopCap counterparts. The only thing notable about the game is that there's a definite ending. Once you've run out of letters, the game gets more interesting, because your goal is to try to scrounge together words from the few remaining letters on the board. The presentation of the game isn't top-notch, but it's fair enough. You'll probably be happier with the alternatives unless you have a particular predilection toward the Scrabble franchise.
