Not for everyone, this ain't an Oceans film.
This one doesn't offer the audience any help. I gave it my best shot and and I am not sure I could adequately explain exactly what occurred. Outside of the early explanation of the "codebook," it's dialogue is very restricted in regard to connecting the dots of both plot and individual character backstory. Nothing is much said that aids the viewers understanding of how previous events are impacting current ones. i.e. how two wives have a connection due to a husbands infidelity, how a man re-enters the now happy life of a woman he lost in order to retrieve an old possession, and how pretending to not remember a woman's name is a lie "over explained.' The acting and direction provide clues, but the viewer has interpret them.
It felt as if everyone involved, actor, director, writer etc, knew that they were doing a bare bones "kind of thing" with this movie. Overall it was enjoyable (I even went back to re-watch a few parts). but I can see where some might write it off as boring, slow, confusing etc.