Earlier this year Amazon released a new firmware for the Kindle that added a "ragged right" justification option.
Now they have added the same option to the Kindle iOS app.
According to the changelog, the v5.12 Kindle app for iPad and iPhone lets users share their notes on Goodreads and it also enables them to change the alignment to ragged right:
For customers who have linked their Goodreads and Amazon accounts, you can now post your Kindle notes and highlights to your friends and followers on Goodreads.
You can now read using left-aligned (ragged right) text instead of justified (aligned on both left and right margin). This new alignment option can be selected from the Display Settings (Aa) menu within Kindle books that support Enhanced Typesetting. On the Kindle eBook Store page, look for "Enhanced Typesetting: Enabled" in the features list.
Speaking as someone who looks for this as a standard feature in my reading apps, I am thrilled to see Amazon finally add it to their iOS app.
It's a pity that this took so long.
You can find the app in iTunes.
image by Marcus T Ward