Dull books - Stop or Carry on?

[Davey S2]

There are a few references in the 'what are you reading thread' from people saying they are 'wading through' such and such a book but finding them really heavy going.

If you start a book do you feel compelled to finish it? if not, at what point do you decide to call it a day?

There have been a few that I have stopped reading (Wolf Hall being the last). Reading is supposed to be enjoyable and if I'm not enjoying it I'd rather move on to something else. I appreciate that some are slow burners and take time to get going but you can usually tell within a few chapters wheher its going to hold your interest.