1. The Train: The train is a recurring motif, representing both the literal and metaphorical journeys of the characters. It symbolizes the constant movement and uncertainty of time, as well as the unpredictable nature of their relationship. The train often arrives unexpectedly, mirroring the way Clare and Henry's lives are interrupted by his time travels.
2. The Blue Dress: The blue dress that Clare wears when she first meets Henry becomes a potent symbol of their connection. It represents the moment they fall in love, a feeling that transcends time and circumstance. This symbol is further reinforced by the fact that Clare wears this dress during their first encounter, even though it's supposed to be a dress she purchases later. It signifies the power of their love to connect them across different points in time.
Remember that interpretation of symbols is subjective, and you might find other elements within the book that resonate with you as symbolic!