update

Author: pangudashu

README.md

@@ -10,8 +10,8 @@
 ## 纸质版
 <div align="center">
  <img src="img/book.jpg" height="280" >
-
- (coming soon)
+ [京东](https://item.jd.com/12267210.html)
+ [当当](http://product.dangdang.com/25185400.html)
 </div>
 
 ## 目录：