The actual screenplay can leave you feeling there are gaps...

Rating: 9/10 (18 October 2018)

... but this is a make-believe fairy tale, and thus expects the audience to accept the simplicity of "and they fell in love, and lived happily forever after". It's not supposed to go into the deep intricacies and nuances of their relationship--she loves him, he loves her, that's it. I think that story-telling, especially fairy tales, ask us to just accept "love at first sight" as being a thing, so you have to watch the film from that perspective--the first time Eliza sees The Asset in containment, she's fallen in love. It's worth noting that all the lives of the characters outside of Eliza and The Asset are not fairy tales--Giles doesn't get the guy, and he doesn't redeem himself at work. Zelda spends much of her time complaining about the dysfunctional marriage she's in, and Mr. Strickland is the most obvious contrast: he's living the literal embodiment of the American Dream, and it tears him apart, makes him evil and sick inside. Then there is Bob, who's trying his best to live out his life as a spy thriller despite being caught, literally, with his pants down. The movie asks you to root for Eliza and The Asset because among all these failed fairy tales they've found theirs, and you want to root for their happily ever after.
It's worth noting that the film comments on their relationship being difficult to understand: Octavia Spencer's character, Zelda, tells her husband that he wouldn't understand the two of them, not if he tried his whole life.
There is one final twist to all of this that just makes the film complete, and even makes the fairy tale make sense . If you have just seen trailers you need to see it to the end.