Here's what I recommend for Piper's major books:
- The Pleasures of God. In an interview years ago, Piper said that Pleasures and Future Grace are the backbone for Desiring God. Read this first.
- Future Grace. I've had a New Year's goal to reread this for several years. I haven't read it because I've been so busy these last 5 years, but I loved it so much that I'm going to return to it this Autumn or Winter.
- Desiring God. I read this first and was underwhelmed. I didn't understand what the fuss was about. I'm sure some of it was that I lacked the required maturity. But some of it was that I read this book first when I should have read the others first.
- Let the Nations be Glad. This is great, but wait until you've read the first three.
How to read Piper.
Read his books slowly, and let his writing marinate. Don't read a chapter here and a chapter there with big breaks between. The effect of reading these books every day for a period of time is so much better. Piper even talks about this in the introduction to Future Grace (he got the idea from Andrew Murray). Read 3-4 pages per day and finish in 2 months, you will be so glad after you read them slowly.
If you want to take it further, read all four of these as a reading project.
A word on reading projects: when I do a reading project, I choose several, if not all, of a writer's books and then read them slowly over several months. I did that for a class with C.S. Lewis and Francis Schaeffer. I've enjoyed doing that with some Systematic Theology texts, and now I'm doing that with N.T. Wright's popular-level books.
I did not read Piper's books this way but highly recommend it. I plan to read these four books as a project starting in the Fall.