I enjoyed the book, and thought the film version was well done, though not totally satisfying -- however, I've found that I've liked it more on repeat viewing. I think that's because I (like most filmgoers) came to it with such high expectations based on the book's truly phenomenal success.
The second movie in the series, Angels & Demons, was actually the first "Robert Langdon" book that Dan Brown wrote. I thought it was pretty good, too, some wonderfully clever, though the movie suffered from the same problem as the book, a convoluted and somewhat silly resolution.
They skipped over making a film from the third book, The Lost Symbol, which was just as well. Much of the book, which took place in Washington, D.C., was reasonably enjoyable, even fun, but it gets sort of messy throughout, and is a total jumble in the third act.
Which brings us to Inferno.
I hated Inferno. It almost gets me gnashing my teeth when I think about it. That's not because the whole book is awful. It's not. In fact, for much of the book it's great fun, with plenty of reasonable twists and turns that author Brown is so good at. Along with a plot twist that is utterly idiotic. But being charitable I could accept that, albeit with gnawing difficulty, since as annoying as the twist is it impacts the story effectively and lets the plot go off in a fun direction. It's the conclusion, however, that is just utterly galling. I won't go into why, so as not to give anything away, but that makes it difficult to explain what bothered me so much about it. But I'll say this -- I thought the last 10 percent or so was thoughtless, lazy and, while certainly full of surprises, a cheap way to deal with the reader. And I disliked it so much that I waved the white flag and lost interest in reading any further Robert Langdon stories.
That's how much I disliked it.
The problem was that Brown set up a story that was difficult to resolve well without more work, perhaps setting things up differently, or taking the time to create more (or fewer) twists at the end to make for a conclusion more respectful to the reader. At least for my taste. I do understand what Brown seemingly wanted to do, and to a certain degree I even respect him for it. But only a certain degree, because if you're going to play around with things, you still need to have it come to an ending that the rest of the book supports.
(Sorry for being cryptic, but as I said, I don't want to give anything away.)
Having said this, I'm not convinced that the movie will end the same way as the book. I think it's reasonable to think that the filmmakers -- fairly sharp people at structure -- are well aware of the issues and would see it's a mistake to go down that path. And I can see them telling Dan Brown that they like his work, but this just won't fly with movie audiences, and we're making a film, not a carbon copy of your book, and things will be different.
There's plenty of precedence for doing such a thing. The movie of The Natural has a very different ending than Bernard Malamud's book. (Rather than hitting a majestic home run that crashes off the light tower, exploding into fireworks and winning the game...Roy Hobbs strikes out.) The classic Rodgers & Hammerstin musical Carousel changed the ending of Ferenc Molnar's play, Liliom, taking a bitter moment when the ghost of the father slaps his daughter in an effort to teach her the harshness of life, and turned it into one of Broadway's most glorious hymns of hope, "You'll Never Walk Alone." (Famously, when the Hungarian playwright came to a rehearsal of the musical, he not only loved the adaptation but added most of all he loved the new ending.) And of course, there are many other examples of films changing the ending from their original source -- for better and, in fairness, for ill.
Whether the filmmakers of Inferno have fixed the third act and changed things, getting them (in my opinion...) right and proper, I have no idea. It's a toss of the coin, but if I was forced to bet (with my heart leading the way) it's that they did change it. As a writer, I want to support the "vision" of the original writer. But since I think Dan Brown got it so profoundly wrong, I'd accept it here.
At the moment, as you might expect, I have no intention of seeing the movie. But I'm going to do something uncommon -- I'm going to ask people who do see it what the ending is. (This isn't a case of "giving it away." After all, I read the book, I know how the story ends. I just want to find out if they fixed it.) And if does get fixed, then I'll go.
I hope they fix it, obviously, for several reasons. Most of which is up to the resolution, the story is pretty good and very exciting (idiotic plot twist aside). And the trailer brings that out. Such a fun adventure deserves an ending that justifies everything that went on before it. I look forward to finding out what they did.
As for the trailer showing the exciting adventure well -- here it is, as you'll be able to see for yourself.