Perhaps you could talk about the 2 people in this poster, the child and the man (who is likely the child's father). The older person represents old worlds, while the younger person represents new (or emerging) worlds, characterised by the imaginative nature of the technological advancements that are represented in this poster.
I believe there would likely be different interpretations regarding what the poster conveys. For example, perhaps neither the older person nor the child represents old words and new worlds respectively, rather they are both on the verge of accessing a futuristic world, which can be seen through the luggage/bag that is carried by the older individual.
Another interpretation may be that the child and the older person actually explore different stages of the life of the same person, meaning that the child and the older person are one person. Them holding each other's hand may be depicting how it all started in the old worlds, which is represented by the child holding a book, and what developments took place, leading to the state that the older person is currently in.
Visual techniques used include the rather low angle shot, which enables us to clearly see both the child and the adult figure, in addition to the landscapes in front of them, including futuristic buildings, streets and vehicles. In terms of how the poster is used to offer a perspective on the imagination and books, it is clear that the direct comparison of the age difference between the child and the adult person, in addition to all the perceived advancements in infrastructure and technology (all of which were made visible thanks to the rather low angle shot), allows for the futuristic aspect of this poster to contribute its own perspective through its imagination and perception of the future of the world and literature.
I hope this helps!