The reason it was discontinued from sale in the first place was due to the game being completely broken on iOS 8.
Square Enix let this lay for a few months before even acknowledging the game-breaking bug. Then, when the time came, Square Enix only said that it wouldn't fix the issue.
This was quickly retracted by the company which then said that it was working on fixing the issue. After all that the game was removed.
Bit of a rollercoaster, that. But, here we are, another bunch of months later, and the game is back on sale. Those of you who already own the game will want to grab that new update, of course.
For everyone else, if you want it, you can pick up The World Ends With You: Solo Remix on the App Store for £13.49 / $17.99.