Never been free before. (Though there used to be a lite version)
From the description
Instapaper is the simplest way to save and store articles for reading: offline, on-the-go, anytime, anywhere, perfectly formatted.
Instapaper for iPhone, iPad and iPod touch provides a mobile-optimized Text view that makes reading Internet content a clean and uncluttered experience.
Instapaper Core Features:
- Save most web pages as text only, stripping away the full-sized layout to optimize for the iPhone and iPad screens.
- Store up to 500 articles on your iPhone or iPad, and store unlimited articles on the Instapaper website.
- Read offline, even on airplanes, subways, on elevators, or on Wi-Fi-only devices away from Internet connections.
- Send to Instapaper from 150 other iPhone and iPad apps.
Additional Features:
- Adjustable fonts, text sizes, line spacing, and margins
- Dark mode and brightness control for night reading
- Automatic Dark and Sepia Mode switching for sunset times in your location
- Sort your list of unread items by popularity, date, article length, and shuffle
Filter your list of unread items by reading time
Folders for organization
- Dictionary and Wikipedia lookups
- Tilt scrolling, page-flipping
- Share via email, Tumblr, Twitter, Facebook, Pinboard, Evernote, or other supported apps
- Rotation lock
- Preview links in the built-in browser without leaving the app
- Search, via in-app purchase
Accolades:
- Featured by Apple many times in the App Store, including both the iPhone and iPad Hall of Fame
- Macworld Editor's Choice Award
- Featured in Wired, TIME, Daring Fireball, TechCrunch, PCMag, TUAW, The Next Web, and many other magazines, newspapers, and websites
Instapaper used to be brilliant, but now it's under new management, and they're currently "fixing" everything good about it. They've made the website slower and uglier, and the IOS client has gained some new bugs.
It's still worth grabbing for free, though.