Although the book has many deeper themes, it can also be read as a simply adventure story. After all, if you think about it, Robinson Crusoe encounters a huge variety of adventures in the course of this book.
Just think about some of the things that happen to him. He is captured and has to live some years as a slave until he can make a daring escape. He then becomes a rich man in Brazil. Then comes the long adventure -- he goes off, and is shipwrecked on the island.
Once he is on the island, his attempts to survive constitute an adventure. He is having to survive in a difficult environment using only his ingenuity and what he could salvage from the ship. As if this conflict with nature weren't enough, he then has to face cannibals. He finally gets off the island and he has a fight with a huge pack of wolves.
In other words, there's all sorts of action and adventure in this book.
Much has been written about themes other than adventure hidden in the depths of Defoe's Robinson Crusoe novel. However, the overall prevailing theme is that of an adventure genre.
By definition the adventure genre is dominated by danger, action, risks and excitement. They take place in unusual settings unlike that which people encounter everyday. The action is fast paced and extraordinary compared to daily life.
Robinson Crusoe contains all of these elements and more. The adventure begins with the wreck of Crusoe's ship and his immediate action to salvage materials that he can use to survive. Each day Crusoe must solve problems and find new ways to survive the elements, hunger and occasional savages. Further adventures have him taming and domesticating wild goats, learning to grow food to survive, meeting a converting a savage named Friday into a companion and helping a group of sailors and captain who arrive to restore order to their ship. They in turn, take Crusoe back home.