Kon Satoshi gained something of a reputation with his 1997 film Perfect Blue as a director who likes to take a, let's say, "liberal" approach to his source material when working on an adaptation. As a result, a read through Tsutsui Yasutaka's original 1993 novel Paprika also throws up numerous interesting differences with Kon's 2006 adaptation. These differences can be summarised under the categories of "structural" and "thematic".
Kon's film is structured more as a mystery and a thriller, with key information withheld or expressed only obliquely until more dramatically opportune moments. The missing DC Minis are introduced right from the get go, Osanai acts as a friend and an ally initially, and Inui seems to be a cranky and troublesome boss, but isn't revealed as the villain until later on. Parallel to this, the characters of Noda and Konakawa are combined into the single character of Konakawa, and his rank in the police force is reduced to that of a simple detective. As a result, the film presents a neat parallel between Paprika's investigation into Konakawa's dream and the evolving mystery of the theft of the DC Minis.
On the other hand, Tsutsui's novel makes it clear from very early on that Osanai and Inui are up to no good. The novel is still a thriller, but it is psychological rather than a mystery. Atsuko/Paprika's enemies are established from the start, and we follow her path through the developing series of plots and machinations at a far less frenetic pace.
Similarly, the connection between Atsuko and Paprika is established explicitly, even to the point of detailing how Atsuko changes her appearance, adding freckles and moving her voice to a more girlish register to complete the disguise, whereas in Kon's film the connection between them is a little more blurred. Kon hints that they are the same person, and eventually states it clearly, but he never explains exactly how two such physically different people could be the same. Is it a physical disguise, or is it a blurring of reality and dreams through the use of the DC Mini? By the end, the two have separated completely, appear alongside each other, and even argue over which one is more real.
How the two versions of the story deal with the boundaries of reality and dreams crosses over into the area of thematic differences. Kon, in the film version's stunning opening sequence, makes it clear that he views the boundaries as fluid right from the start, whereas Tsutsui breaks them down at a much slower, more measured pace. For Kon, with that opening rush through clips of The Greatest Show on Earth, Tarzan, Roman Holiday, and a spy thriller that might be From Russia with Love or possibly North by Northwest, the breaking of those boundaries mirrors the way the audience of a film set aside one reality and step into another, as well as the way the director of a film takes a world from his own imagination and recreates it as an entirely new reality on the screen.
In Tsutsui's novel, cinema is certainly a minor theme, particularly in Noda's dream, but he seems much more interested in the details of mental illness and psychotherapy (which Kon largely glosses over), and in particular issues of sex and sexuality. There are some sharp observations about the way Japanese society frowns on attractive women also displaying obvious intelligence in public, but mostly sex is portrayed as the battleground where the novel's competing philosophies slug it out.
The homosexual relationship between Inui and Osanai plays out as faintly abusive one, based on power, and throughout the story, Osanai shows himself unable to view sex outside of expressions of power. Atsuko, portrayed here as much more sexually assured than her equivalent in the film, has a much more empathetic attitude to sex. As Paprika, she often forms close attachments with the patients of her dream analysis, and on one occasion actually has sex with Konakawa in a dream as part of his therapy (compare with the slap across the face she directs at him after he kisses her in the film). Towards the end of the film, as the dream world and real world merge, she is happily engaged in concurrent sexual relationships with three different men, often all at once.
The collision between Atsuko's empathetic approach to sex and Osanai's power-based approach comes in a scene where Inui directs Osanai to rape Atsuko. Osanai, confident in his good looks and desirability, is convinced that all he needs to do is force himself on her and she will become subservient to him. That all he needs to do is "break" her. Unable physically to resist, Atsuko resigns herself and in fact decides to use it as a chance to work off some of the physical need for sex that she hasn't had time to act on because of her work. However, once she shows herself willing to act as a proactive partner, Osanai finds himself unable to sustain an erection and is forced to beat a humiliating retreat. Even then, Atsuko chides herself for mocking his sexual inadequecy and not empathising with him more.
Finally, with Inui, the main villain, there are key differences. Kon portrays him as an old, crippled man who wants to use Osanai's young, attractive body to renew himself. In the novel, there is an entire subplot that is absent from the film, dealing with Atsuko and Tokita's nomination for the Nobel Prize and Inui's jealousy after he lost out to a British scientist many years ago. The battle lines with Inui, however, remain the same as with his protege Osanai. Power and domination versus empathy and understanding, brainwashing versus therapy, and interestingly Christianity versus Buddhism. Inui's dreams are deeply infused with European, particularly Christian, imagery. As Tokyo descends into chaos, mythological creatures from ancient bestiaries do battle with Buddhist deities in the city streets. Inui takes the form of the demon Amon, quotes lines from the Jesuit training manual, summons griffins, and creates vast cathedrals from nothing, while the two barmen, Jinnai and Kuga, battle them as Acala and Vairocana.
Singling out which is the better of the two is a pretty much meaningless exercise and the two are different enough that you could enjoy both without one ruining the other for you. The fact that Tsutsui himself appeared in the film as the voice of Kuga (acting alongside Kon himself as Jinnai) suggests that he had no problem with the hatchet that Kon took to his story, and it's obvious reading the novel why the director of such films as Perfect Blue, Millenium Actress and the TV series Paranoia Agent would be interested in it.
There are definite issues (possibly on the translator's side) with the quality of writing in the novel, particularly the way it hammers away through the third person narration at points that could be better expressed more subtly through the characters' actions; but perhaps the most unusual point from the point of view of Kon's back catalogue and Tsutsui's novel, is the way the film version shies away from the most controversial aspects of the novel. Tsutsui followed the release of Paprika with a three year self-imposed strike in protest at the Japanese literary establishment's squeamishness around taboo issues like mental illness. However, despite Kon's track record of touching on controversial social issues such as suicide, homelessness, prostitution and Japan's militaristic past, the film version of Paprika is mostly shorn of the novel's most pointed aspects. As it stands, Kon's film is a superb fireworks display of postmodern cinematic trickery, in some ways influenced more by Godard and Truffaut than it is by Tsutsui's novel, but lacking a lot of the meat of its printed forbear. In a sense it can be said that Paprika (1993) is a triumph of the "what", while Paprika (2006) is a victory for the "how".