It's a shame Lyne and Rubin didn't team up again... This is the kind of movie that is sorely missing from today's theatres. While numerous directors and writers (too numerous to count) are trying to take horror films in new, original, and relevant ways, Jacob's Ladder will stand the test of time as a cult film that is truly terrifying and goes the extra mile by containing both criticism of military politics and an incredibly dense emotional subtext, none of which overwhelms the final product.
Current horror films take the concept of gore, jump scares, and soundtrack to the utmost extreme, sacrificing mood, tension, and restraint, which are the biggest assets to a horror film. Jacob's Ladder utilizes every tool in the horror palette that it needs while remaining true to its own ethos. The best scene to fit this example is the party, where one of the characters quite literally dances with a demon. In a more contemporary horror film, we would clearly see this demon, shots might be in slow motion to emphasize the sexuality in it, we would probably get creepy soundtrack music, the character in question would probably get torn apart, and at least part of the demon would likely be CGI.
Instead, the demon is seen in flashes that are quite unclear, which gives the viewer the idea that what they're NOT seeing is more terrifying. The sequence takes place in real time with appropriate dance music in the background without sacrificing the sexuality and the meaning of what is happening; this gives it a more realistic feel to the viewer. All the visual effects are in camera, but never in the same shot as the protagonist, offering a distance that allows for interpretation; is what the protagonist seeing reality, or an illusion?
This one scene (which is by no means a plot spoiler) is indicative of the technical, formal, and metaphorical mastery of this film. The explanations for what is seen in the film are critical without being overbearing and toe the line for believability while leaving space for interpretation. The mood conveyed by the film is consistently dark, darker than most any other film could hope to achieve. It's so dark, in fact, that a large majority of people were practically catatonic leaving the original cut of the film.
This film fires on all cylinders; the directing, writing, acting, music, special effects, production design, message, mood, and tension are always kept exactly where they should be. Simply put, it's a dark masterpiece.