With the many enjoyable books that I have read, I have to say that my favorite is "El Ingenioso Hidalgo Don Quixote De La Mancha" (Translated: "The Ingenious Gentleman Don Quixote of La Mancha"), by Miguel de Cervantes Saavedra.  A contemporary of Shakespeare, Cervantes is often considered the founding father of the novel.  During his day, there were many works of chivalrous fiction being composed in his day, and treats specifically to the creation of these works and their impact on society.  In fact, it could be said that Don Quixote is novel which is a spoof on novels, and the concept to me, in and of itself, is pure genius.  His implementation is remarkable as well, and the work is highly regarded.  In one survey of 100 authors, it was often considered to be the best novel ever written.  I have read it both in Spanish, and also in English.  While a book of this scope plays out much better in the romantic language in which it was penned, it is highly enjoyable using John Ormsby's very faithful translation to English as well.