Anything by Terry Pratchett, I suspect. I tried a few based on strong recommendations and gave up every time. In a similar vein, Hitchhiker's Guide to the Galaxy (I may have finished this one in my younger years, but definitely gave up on the sequels). They're just not me. Try as I might, I can't find them either funny or interesting. To be honest, any kind of 'fantasy' novel is a bit of a no-no, from Harry Potter through to LoTR. My boat isn't floated.
Louis de Bernieres. Good god, I can't remember the book, but it was awful. I was like wading through some kind of sludge extracted from the brains of failed English literature students. Anything else dug from the midden of overwritten, meandering 'literature' beloved of broadsheet review pages, for that matter. I can appreciate some of it may be well-written, but it's like eating a block of butter with a spoon.
Finnegans Wake. That was a bit of a watershed moment when I realised life was simply too short to read books because I thought I should (or because I'd look clever and girls would sleep with me), rather than because I wanted to.
Hmm, there's also a copy of Robin Lane Fox's The Classical World that's been sitting by the bed for about two years. I got about half-way but despite it being the kind of book that should float my boat, I find strangely tedious for some reason I can't put my finger on, it's just very spotty and has that off-putting Oxbridgy knowing tone. I suspect I'll never get to the end before it falls victim to one of my wife's tidying massacres. I've rescued it a few times, but I think the next time, I let it die.
Jared Diamond. Tried and died with two of his, both were like an endless geography class where the teacher keeps reiterating the same conclusions over and over, seemingly in the belief that in the last fifty pages the reader would have forgotten everything that had gone before. Understandable, my brain had climbed out of the window and gone to play in the park.