Live-Poll: Unfilmable

FYC:

Watchmen (2009)


Cloud Atlas (2012)


Fear and Loathing in Las Vegas (1998)

@Breumaster,

For your consideration:

This time, I let the profile-links of the users away, because when anyone wants to visit one of the suggesters, he can search through my 80 first polls, I linked in my profile.

@Breumaster,

For you consideration:

Great idea, Breu! 

May I suggest a few small edit? (below in bold)

There have always been books which forced the impression to be unfilmable. But then some producers, directors, and actors came and showed that the stuff is not unfilmable. We all know that the 'Lord of the Rings' franchise was one of these "so-to-say" big unfilmable ideas, but at the end it became a highly acclaimed movie series.

I'd suggest replacing "actors" with "writers." I don't know how much actors really have to do with it but writers are essential at that stage and to adapt an "unfilmable" book or concept to the screen. Also, I'd probably remove "smaller" from the question? Several of the options are pretty big movies and concepts, too. 

Oh, FYC: Jaws! It took Spielberg so long to convince someone that he could do it and, ultimately, it was so close to never being made.  The mechanical shark wouldn't work and the production went way over budget and way over time -- well, I'm sure you know the story -- for the 1970s, it was an incredibly ambitious project that almost everyone said it was doomed from the start. 

Another FYC: The Invisible Man (2020)

FYC: Ulysses (1967) based on James Joyce novel

Catch-22 (1970)

Naked Lunch (1991)

Source for the three above

Since you are including upcoming projects, there seems to be an upcoming tv series on 100 años de soledad Probably the best novel on Latin American magical realism, but that it certainly is difficult to put on the screen.

Also Tristam Shandy - Source

I finally re-arranged the order of the options a little. Ready to go.

FYC: Life of Pi

Congratulations, @Breumaster!

Unfilmable

Live Poll: https://www.imdb.com/poll/zwJJaGKcR5Q/

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FAQ: Updating Threads After Poll Goes Live

Not very good options.  From reading the book, some seemed perfectly simple to film, in particular the two in the lead.  Jaws and The Shining.   Neverending Story felt like watching a film when i was reading it, so was also perfect for adaptation.

EDIT:  Having read the comments, i see that some people have suggested books due to the number of characters or locations, or even difficulty sourcing set/design factors.
   I was thinking more of the complexity of the narrative and difficulty in transferring concepts to the screen.  For which my own recommendations would be The English Patient (don't bother reading it), and American Psycho.

For those that have read the book of Perfume (which is quite difficult in itself), a film adaptation seemed a very great task.  

How about A Clockwork Orange? From critic Simon Braund:

Ethical screed aside, what does A Clockwork Orange have to offer beyond its curiosity value and a crash course in humanism? Well, for a start there's Kubrick's dazzling visual style which, rather in the manner that Trainspotting did 25 years later, translates the substance of an "unfilmable" book into the language of cinema.