1) You're wrong about the lack of texture on the blue books. I only changed the title of the book, the texture is the same. I have attached the previous image and the last one to compare.
2) I increased the "Commemorative Gold Edition" a little. It is impossible to make it equal to the size of "The Wizard Was Odd". The name of the book and the trilogy are priority and we can not change the semantic structure. I made two versions, but I like more the Book Version 1 (the inscription in one line).
3) The Oz logo was made specially in conjunction with the lightning and the sky and it is already very large in size. Do you want to put the logo together with the lightning on the back cover?
4) The purple background image that you have downloaded from the site has a high graduation (light & shadow). Obviously, this is an amateur photography of the texture. I have attached the "Sample. Jpg.", Where I took the rectangles and move them to other places to see the difference. Probably, the one that at the center is closest to the real color. However, the exact color is not clear because of poor sample. I have attached the "Sample 300dpi. jpg" to see the low resolution of the texture. To make high-quality images I need to have a high resolution texture or create the texture based on the sample myself. I can do this texture well if you want and it can be used for advertising of the book.