A nice feature introduced in iOS9 is the ability to convert an article from a Web page to PDF format and save it to iBooks. This comes in especially handy if you come across a lengthy article on a web page that you want save and read later on when you have more time.
When you find an article that you want to save in iBooks, click the Share icon on the top right corner of the Safari window.
From the Share Sheet, tap Save PDF to iBooks (you may have to swipe from right to left to navigate the sheet). The PDF will then open in the iBooks app.
If you use this feature often, you might want to move it to the beginning of the Share Sheet for quick access. Click the Share icon on the top right corner of the Safari window and tap More (the last entry in the Share Sheet). Scroll down until you see the Save PDF to iBooks icon. Click the move icon and drag upward to the desired location in the Share Sheet.