Yes, parts of the book are boring (e.g., lengthy poems), but the majority of it is hilarious. Don Quixote is such a loon but at times sounds perfectly normal. My favorite incident is when he paranoically destroys a puppet show. Sancho Panza is unfailingly funny. I love this book.
I was pleasantly surprised by the high quality of this book. The plot is complex and original. It's a page-turner. I'm now reading the followup book, Baron Trigault's Vengeance.
I read this based on the recommendation of kveto of prague. I wasn't disappointed. I will simply second everything she (?) said about the book.