There are a few ways in which we can answer this question. In a work as long and complex as this one, it is hard to give the essence. Moreover, all people read texts differently. However, if I had to give the main point of the work, I would say that it is about homecoming through twists and turns. The idea of homecoming is the main objective for Odysseus and as he tries to do this, there are many twist and turns in almost every book. Homer even give the reader a heads up on this point as book one opens with these word to describe Odysseus: "man of twists and turns."
As we look at the the epic from a broad overview, we can see that there are many unplanned adventures for the hero. He has to overcome the sirens, rescue his men from Circe, who has turned them into pigs, Polyphemus, who wants to eat them, and Calypso, who has him as a love prisoner. We can also mention the fury of Poseidon who has no love for him for blinding his son, Polyphemus, and the vile suitors, whom he has to defeat to rescue his wife and homeland. Nothing come easy for Odysseus.
In conclusion, Odysseus has a journey to accomplish, but this journey will be completed with many twists and turns.