I've started so I'll finish

Many years ago, back when I was a starving student, I was huddled in my miserable garret room reading Robert M. Pirsig's Zen and the art of motorcycle maintenance. It's one of those books which always makes the classics lists and I felt I ought to read it, but as it turned out I can't recommend it as an experience. I can only describe it as the literary equivalent of whacking yourself in the knackers with a bag of frozen peas, and as I sat reading I'd occasionally look up from the page and mutter to myself "But that's complete bollocks" before pressing on.
Eventually, about midway through the book, I got to a lengthy section about the concept of 'quality'; as I recall it's about how quality is something that everyone recognises but cannot be formally defined, and that makes it different to everything else ever. At this, I finally succumbed to my rage and with a terrifying roar I hurled the book through the window* and never bothered going to get it back. It sat in the front garden for a few days until someone nicked it.

This was the first time I can remember not finishing a book. I normally feel there's something of a matter of pride at stake to finish a book when I've started it, which has resulted in my forcing my way through all kinds of cobblers - I've read the entirety of Les Miserables, including the brain-melting tedium of the 100 pages of Marius in the middle. I've read Atlas Shrugged, including all of John Galt's speech in a single sitting. I've even read Conrad's Quest for Rubber which, suffice to say, isn't as good as the title might at first imply.

But since that liberating day with Zen and the Art of Motorcycle Maintenance, I haven't felt utterly compelled to keep reading no matter what, and so the list of books I've never actually finished slowly grows. I've never finished Dante's Divine Comedy because it just gets a bit boring after the Inferno. I've never finished Douglas Hofstadter's Godel, Escher, Bach because I'm just plain not clever enough and I feared that if I persevered they might find me in a slum twenty years hence surrounded by the detritus of a wasted life** still on chapter twenty trying to work out logical propositions. I've even not finished the Bible yet, because the Old Testament is filled with exciting begatting and smiting*** but that all comes to a screeching halt with the New Testament and being nice to each other - which is never as much fun.

Anyway, that's the question for the day - which books have you failed to finish, and why?

^{*Fortunately it was open at the time
**Like they won't anyway.
***Like my favourite films.}