First I read the book, then at the weekend I saw the original movie adaptation in Swedish and then on Wednesday I watched the US adaptation. I have to admit, the US adaptation was wilful perversity on my part. There's a point at which diminishing returns set in as you try to understand different takes on the same idea.
The book is, on balance, the most satisfying version of the story. With translations it's hard to tell whether you're reading good writing or a good translation (so I don't know if I'd hate the Millennium Trilogy the same way if I could read it in the original Swedish) but the English translation of the book is a good read, well written and atmospheric. And with 480 pages to work in, Lindqvist is able to bring all his characters to life and create a fairly detailed and rich evocation of the Stockholm housing estate in the 1980s which forms the background for the action. Movies have to get the job done in the equivalent of no more than 150 pages, and everything you put on the screen costs money. Every character is a cost; that's one of the major differences between books and movies. A movie will always reduce and condense the dramatic personae of a book.
Both the movies strip the story down to its essentials; lonely boy meets child vampire in rundown housing estate, gradually realises that the child is a vampire, and eventually runs away from his miserable life into an unknown future with the vampire. Everything that isn't essential to putting this across is cut away. What's left in the movies is satisfying in different ways, but if you've come to them having first read the book, you're acutely conscious of how much has been lost.
The Swedish movie was scripted by Lindqvist, and he tried to keep as much as he can of the wider world of the estate. Major subplots involving the lonely boy's mother and the police got carved out completely, and the parallel track of the indigent drunks, who are both the main victims of the child vampire and the only people who come close to figuring out what's going on, is cut back to the bare minimum; instead of the deeply realised characters of the books, we get quick sketches of recognisable types. The same thing happens with the school bullies who in the book have a much more complex back story and a more ambiguous relationship with the boy; the trio of bullies get knocked back to simple bully stereotypes. It had to be done, really. The main story needs all the room it can find, and there's just no room for the complexities of the book.
The US version strips things down even more. The Swedish version kept the boy's father as an actual character, but the US remake cuts him back to a voice on the phone, and the neighborhood deadbeats lose their identities almost completely. Their role as the de facto investigators of the vampire killings is taken over by what appears to be the only police detective in Los Alamos. Setting the US version in 1983 Los Alamos is a weirdly inspired move because we never see Los Alamos in the movies and when we do, it's not covered in snow. Somehow, it looks like the last place in the world anyone would ever want to live. It's actually grubbier and more downbeat than social housing in Sweden, but then again, Sweden's probably a nicer country than the US to live in if you're poor anyhow.
So those are the gross differences. Read the book if you want to get a deeper and more involving story and a much stronger sense of how Sweden ticks. Watch the movies if you want to see a vampire story about kids which isn't really suitable for kids. Both movies keep everything low key and simple; if you buy the idea that vampires are possible, everything else makes perfect sense. Life as a vampire comes across as tough and empty and depressing - life as a vampire's minder comes across as even worse. Yet the life of a lonely twelve year old boy beset by bullies and with no friends and a family that's falling apart can make even life with a vampire seem like a better deal than hoping that his life will get better if he stays put. Far more than the book, the movies work to the extent that the child actors can sell their characters.
In the US version, the boy (Owen in the US version) is MUCH creepier than the boy (Oskar) is in the Swedish version - which is much less true to Lindqvist's original character. In a way, it's easier to imagine Owen going over to the dark side than it is to imagine Oskar doing it, because in the opening moments of the movie, Owen already seems halfway there as he spies on his neighbors while wearing a Michael Myers mask. Oskar seems sad and lost; Owen seems like he's got a good chance of being a serial killer when he grows up, even if Mother Theresa turns out to be the new neighbor.
And then there's the vampire; Eli in the Swedish version, Abby in the US version. I think that Chloe Moretz is this decade's answer to Christina Ricci and Natalie Portman, a child performer with such ridiculous poise and charisma that almost anything is possible for her. And I have to admit that I was a little irritated that she took up this role. In a few short years, she'll be an adult; the time in which her unique ability as a CHILD actor can be used is terribly limited. To throw it away on a remake ... but as John points out, it's not as though there are a huge number of roles for children in the first place. And I have to be fair. It's an interesting challenge for a child actor. Weirdly, I think that Lina Leandersson in the Swedish movie shades it, because she's a more ethereal looking actress and somehow conveys a greater sense of alienness (though I discovered just now that her voice was too high, and they dubbed in an actor with a deeper voice for her lines, which may account for some of the distancing). Moretz is GOOD, don't get me wrong. She can't not be good. But her Abby is not quite as out there as Leandersson's Eli.
Both movies pull their punches on key icky bits in the book. In the book, Eli/Abby's minder is a pedophile who Eli has hooked in and enthralled while keeping him at a distance physically. In the Swedish movie, the pedophile element was dialled right back, and in the US version it was removed altogether - though I actually liked the revision because in one minor shot, we see that the minder was once a child Owen's age, and he's grown old trying to help the unchanging girl he loved; that one shot (of a faded photograph) presages Owen's future, and we get to see Owen appreciate this and still later accept the price. There's something very strong and sad in that moment. The other pullback is that in the book, Eli isn't a girl at all, but a boy who was castrated before being turned to a vampire. The Swedish movie doesn't explain the back story, but in one quick shot shows the mutilation as Oskar watches Eli change into his mother's dress; in the US movie, the same scene doesn't show the scar; I suspect it's going to be a deleted scene on the DVD because the whole scene is set up for the same reveal, yet it doesn't happen.
These are things which probably only matter to someone like me who's overdone his exposure to the whole thing; really, all three versions are solid work. I like it that both the movies keep things very simple and light on special effects; the climax, where Eli/Abby rips the bullies apart in a swimming pool, is done very simply in both movies, with Oskar/Owen being held below the water and seeing only bits of body falling past him. Cheap to shoot, but also a great way to show the violence without showing it.
The films work because the love story works, which works because the actors - all four, in the two different versions - do a fine job of getting us to buy into their loneliness and need for each other. That's the heart of the thing; that's what makes them worth seeing. But it's worth pointing out that the US version also made John jump a foot in the air when the investigating cop meets his untimely end. A movie is doing good work when that happens.