I vaguely remember seeing the film, way back in the day. The book it's based on is superbly written. Katharine Topkins knows her way around Eng Lit. She's as good at setting scenes/dialogue or subtly delineating a relationship between a 70 year old man and a pregnant teen.
This novel is no Lolita story although it touches briefly every now and then on the same theme. Both Kotch and Erica are societal outcasts in a sense (one due to old age and a future in an old age home, the other a young pregnant teenage girl) and both have to come to terms with their place in the world. In the short term however they strike up a relationship (platonic) that suits both their needs. Erica is a resilient, determined, capable feminine role model. No less so Kotch in the vanguard of his life.
Beautifully written, unfairly neglected now, indeed Katharine Topkins appears to have fallen off the edge of the Google universe bio wise. Her other novels based on the skill displayed here would seem to be worth investigating.