Pożycz książkę and other 68,800 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
The icon is shaped like a square with the top left corner being curved and the top and bottom right side corners being pointed. The bottom left corner curves into a oval shape that runs the length of the square but doesn't close at the end. Inside the square is an arrow pointing down with 3 dots at it's tail.