I made a dozen book covers as Christmas presents for my family and friends.
It was a long project (I started during summer) and the design evolved a bit - I tried different sizes and I adjusted the position of the bookmark, in some of them I even removed it completely.
In the beginning, I tried to make them quite big, so they could adapt to different kinds of books. The results were not ideal, because trying to fit every book meant that they were a perfect fit for none of them.
After trying different sizes, the one I liked more was the one for a small portable agendas, even if it was smaller than the others and I had less space for decorating, I liked the idea that this was a fixed model and I could reuse it every year, as long as I buy the agenda of the same size. This model had no bookmark, since it was already included in the agenda, but I find really useful that it's small enough to fit in a pocket and easy to carry.
I experimented with different color / fabric combinations and I am really pleased by the results, I could really not decide for a favourite.
Special guest, a book cover decorated with cross-sticht for my sister: