Sure. 'The Unlikely Pilgrimage of Harold Fry' is a novel that features an older couple in an interesting way. The story is mainly about Harold's journey, but his relationship with his wife is an important aspect. Also, 'The Rosie Project' has a main character who is a bit older and his romantic journey is quite engaging. And 'Me Before You' has a relationship aspect that can be related to older couples in terms of the depth of connection and change.
There are several wonderful older couples romance novels. For example, 'Outlander' series by Diana Gabaldon, while it has a lot of historical and adventure elements, also has a strong romantic storyline between an older couple. The way their relationship develops over time is really fascinating. Then there is 'The Light We Lost' which shows how love can endure and change over the years for an older couple. 'One Day' also has elements that can be related to the love story of an older couple as it spans over a long period of time, showing the evolution of their relationship.