To create a cohesive series, the overall frame of each book will remain consistent, but the color of the frame will change according to the element represented in the book, such as fire, air, darkness, and so on. Additionally, the images within the frame will also correspond to the specific element of each book. This approach ensures that each book stands out and has its own unique visual identity.

One of the advantages of this concept is that when all the books are displayed together on a bookshelf, the variety of colors in the frames will immediately catch the eye and create a visually captivating collection.

I believe that this design approach not only provides visual interest for each individual book but also enhances the overall aesthetic appeal when the series is showcased as a whole.