I think the English translator must have been better than the original writer, because most English speakers I have met who have read this walked away with a positive impression. In Portuguese, Coelho often comes across as barely literate.
This is two books which alternate from chapter to chapter. The first book is about a boy looking for treasure. The second is a self-help book for narcissists who worry that they are not self-serving and manipulative enough. In the end (spoilers), the boy finds where the treasure should be buried and starts digging. Pretty soon he gives up and decides the actual treasure was the experiences he had along the way. Then he digs a bit more and finds some gold and gems and decides that the real treasure was actually getting really rich.