Well, my 2p worth... "Jonathan Strange and Mr. Norrell" by Susanna Clarke is quite probably the first book that I've bought on someone else's recommendation, only to be defeated in actually completing it. I nearly expired with boredom and could draw on further determination to finish it.
"Labyrinth' seems to be a popular choice, and I would agree. This was another rambling... forever rambling... novel that I really wish I hadn't bothered to purchase. I seem to remember that somewhere mentioned that it was quite possibly the book most bought, but least read(?)
I have to say that I'm somewhat sceptical when I see the strap line 'International Bestseller'.
I'll always be completelt incredulous that 'White Teeth' got into print yet alone won acclaim (although even 10 years later I feel that even a lot of its original supporters may feel embarrassed by it now). The premise is ridiculous and the author can't even write decent English.
The point some of you are making that the book 'The Time Travelers Wife' is unrealistic is moot, it's fiction for a reason and I think both protagonists are fascinating characters, I struggled to put it down the first time and I'm now on my fourth round, my favourite book by far