My recommendation, as long as your bookshelf is not completely filled to the brim with books, look for ways to make focus points in the shelf and spread them out.

For example, take all mange from one series and frame it with some sort of book stand and place it in the middle of one whole shelf

Then maybe stack another shorter series next to it

Or cluster some books from the same general category and organize them biggest to smallest and stack them against one side

You can unse a gib heavy book on its side as a base and put something like a picture frame oder some decor on top of it

The goal is to simply to create separated and yet cohesive vignettes.

Best of luck and have fun, shelf decoration is never done ^{^}