Here a review coming from someone who hasn't completely finished it yet, so take my answer with a grain of salt.
Don Quixote is definitely a great book, although it definitely has its flaws that hold it back from being one of my favorites. Even still I love this book and look forward to that part of the day in which I can sit back and read for an hour.
Pros - Don Quixote is one of the funniest books I have ever had the pleasure of reading. Most of its humor however can't be understood because it heavily relies on references and common knowledge of someone from the 1600s. I STRONGLY recommend the translation by Edith Grossman because it contains notes explaining some of the novel's more obscure jokes.
Don Quixote has probably my favorite main character in any book, Don Quixote, who drives most of the plot.
Cons - The book can be really slow at times, I'm talking incredibly slow. If you aren't able to wade through some of the more boring sections of the book, I wouldn't recommend this to you. I'm particularly reminded of a scene where people try to decide which 500 year old books should be burnt, it has no relevance to the plot and takes up ten long pages.
The book contains a ridiculous amount of beating, I challenge you to name a book in which the main character is beaten to a pulp more than in this book (which I count 5 times so far) and it's described in detail. If you aren't prepared to have the lovable main character have his ribs bashed in, mouth cut, and vomiting at the same time, then this book isn't for you.
Overall this book is still a great read, but the cons are strong enough to knock it down a star for me personally.