The worst books I've had to read in English was Pride and Predjudice and Jane Eyre.
Pride and Predjudice was easy to understand plot wise because I've seen the movie on tv at least three times, but when searching for quotes that might appear on the test the next day and memorize them for context and speaker out of a thousand possibilities, it sucks.
i]Jane Eyre[/i] was at least entertaining, but same deal, and not too entertaining.
Although Shakespeare's Macbeth is the best book we've read by far, it has killing, it has madmen, it has an actual plot. Compared to the girly plots of Pride and Predjudice and Jane Eyre, in which the characters just talk, show indignation, grow fond of each other, become affectionate, break up, reunite, and everything works out the same way, for every friggin' book. At least Shakespearean books have murder.