Maybe you don't know what to read. Maybe you have too many books to read. Maybe you are stuck in a reading rut.
C. S. Lewis suggested that we alternate reading old books and new ones. I'd like to tweak that just a bit. My suggestion is that you always be reading a couple of books at a time - one old and one new. I've found that this method keeps me interested and challenged.
Right now the old book that I am reading is The Bruised Reed by Puritan Richard Sibbes. Old books usually take longer to read than new ones because the English language has changed over the years. However, the good old ones are almost always very rich and worth the effort.
As for the new, I just completed John Piper's Jesus: The Only Way to God. I'm now going to start Mere Churchianity. This book was written by the late Michael Spencer (formerly the Internet Monk). I don't know if I will like this one but I know it will force me to ask myself some hard questions. Sounds good.
So read something old and something new. Don't concern yourself with reading anything borrowed or blue.