Finally, Google Reader has reached the end of its (product) life. It has been a good companion for a long time. I still cannot understand why Google wanted to discontinue this product (although they have tried their best to explain). However, I do not believe usage has declined.
Please read the FAQ to see what you can do. You have until 15th July 2013 to use the Google Takeout function to backup your Google Reader info. As for substitute for Google Reader, I am using Feedly now and Digg Reader is also a good choice.