Night Waking was first published by Granta in paperback in 2011. There also exists a Kindle edition and a translation. It also appears that different covers have been used in different editions, possibly due to attempts to market the book in slightly different ways in different countries. In order to write a comparative study of the cover art for the different editions and other elements of the books as material object that might differ from edition to edition, you would indeed need to obtain copies of all print and electronic editions of the book. Research on the postgraduate level must always be comprehensive.
Because the novel is relatively recent, there is little if any scholarship concerning it, though there are several published book reviews. One starting point for talking about paratextual studies would be Examining Paratextual Theory and Its Applications in Digital Culture by Nadine Desrochers.
Your paper should begin with an argument concerning how and why the editions of the book differ. You might look at whether market segmentation, format, or region are determining factors.
The second section of the paper should describe the book's full publication history, including all editions and printings. For each edition, you should provide a complete bibliographic description.
The third section of the paper should compare and contrast the different print editions, looking at such features as cover art, format, paper quality, price, and other changes between editions.
The fourth section of your paper should examine the differences between the print and digital editions. Here, you might include both a discussion of conventions of Kindle formatting which apply to most books published on Kindle and issues pertaining to this individual book. You should finish this section with a discussion of how the electronic versus print differences affect reader experience.
Your conclusion should talk about how the physical natures of the different editions create differing horizons of expectations for readers and how this would affect how we interpret or approach the text. Reader-response criticism might be a useful scholarly perspective for your conclusion.