This was a movie version of the first of Donald Westlake's Dortmunder series, with Robert Redford in the lead. Having read several of the Dortmunder books (but not this one), I did come in with a mental image of the characters in my head, and these actors didn't really match up. Dortmunder is supposed to be this relatively pessimistic dour character (and is even described as such here), but Redford seems a bit too active and physical for my mind here. But even so, it's an easy, winning performance that I suspect he pulled off on a regular basis at this point in his career (I'm not a big fan, so I haven't seen a lot of his work). The other characters were OK, although the loss of the character Tiny from the novels was missed (although he might have been added later in the series).
The Dortmunder books typically involve the identification of a theft target and then a series of increasingly complicated plans to acquire the target in the face of new obsticles. This movie is no different, as the crew has to run four separate operations in order to get to the titular diamond. Again, I don't know if the plans here match up exactly with the novel's versions, but I wasn't particularly impressed with either the third plan (involving a novice helicopter pilot and an assault on a police station) or the fourth (using a hypnotist to get inside a safe deposit box) - neither of them sounded like typical Dortmunder plans. So, as a Dortmunder movie, I didn't find The Hot Rock very satisfying. But as a basic, no-frills comedic heist movie, it's OK. Three stars.