As with many best sellers, this was later made into a movie. As is often the case there are significant differences between book and film. But both are enjoyable - just be aware if a movie viewer is discussing this with a book reader, you will not have identical memories. That said, the differences may be the least of your issues. I confess that my impression was less than stellar, which is where another book comes in.
The SHACK Revisited is by C Baxter Kruger, and on the cover, he says "There is more going on here than you ever dared to dream". This may be a play on a key aspect. This author is a theologian, but don't let that spoil the adventure ahead. Of course quite likely you're different from me, and The Shack may have been satisfying enough, but for me, at first it was fairly ho-hum. After this unpacked it, it made much more sense.
Of course, I was in the midst of rethinking my theology. The portrayal of the Father as a Negro woman at the start didn't throw me terribly, but my conservative theology struggled with the book. My independently "revised" theology handled it much better.
Much of that theology came from Harold Eberle (also supported by Tom Wright). In this video, Eberle and Young are hosted at a church in the US where they discuss their theology.