The length of the novel can be a turn off. However, this is akin to saying a couple seasons of a sitcom is longer than a movie. You could read just the first bit of the books and have a sufficient conversational understanding of Don Quixote. The additional chapters cover additional humorous episodes that further develop the characters. I found Sancho Panza to be the most intriguing. He is both dumb and whitty. He realizes that Don Quixote is crazy, yet he goes along with him anyway, in hopes of getting his great reward. He does get a taste of being a "leader of an island", but tires of it. However, in the process, he actually is a good leader.
Many of Don Quixote's friends try to help him with various ploys. However, none succeed. People do write about his exploits. In multiple occasions, Quixote and Sancho encounter people that have knowledge of them through the stories or written works. They try to correct their misunderstandings - but this often ends up displaying them in worse light.
There is so much to the novel, it is easily worth another long reread.