Contact reports rarely sit comfortably in any single category, and Dimensions is filed with us under religion and spirituality, which is itself a kind of argument. Jacques Vallee is listed here through that title and through the sequence it belongs to, the Alien Contact Trilogy, a framing that says plainly this is sustained work rather than a single provocation.
The filing places the material alongside belief and testimony rather than alongside popular science, and the difference is not cosmetic. It moves the question away from what happened and towards what people report, and what they subsequently make of it.
Twelve hours, with a trilogy standing behind it. Whatever else may be said, this was not written to be skimmed.