One way to distinguish is through the way they handle social change. Victorian novels showed the impact of industrialization and social reforms on society. They were often a bit conservative in their view of change. Modern novels are more likely to embrace and explore radical social changes, such as the digital revolution. Also, the structure of the story can be a giveaway. Victorian novels often had a more straightforward structure, while modern novels can be very experimental with structure, like using multiple timelines or unreliable narrators.
The portrayal of women is a key aspect. In Victorian novels, women were often depicted in traditional gender roles, like the angel in the house concept. In modern novels, women can be presented in a much broader range of roles, from strong leaders to complex individuals with diverse identities. Another difference is in the pacing. Victorian novels sometimes had a slower pacing with detailed descriptions. Modern novels can have a faster pacing, especially those in the thriller or action genres.
Well, you can look at the language. Victorian novels generally have a more archaic and formal language. For example, they might use words that are not so common nowadays. Modern novels use contemporary language. Also, the settings are different. Victorian novels are set in the Victorian era, so you'll see things like horse - drawn carriages and gas lamps. Modern novels can be set in any time from the 20th century onwards, including futuristic settings.