- When not all the books in the series are the same height.
- When books change covers with editions so they don’t all match unless you buy the series in one go.
- When some books are hardcover and some are softcover and it doesn’t match but you can’t find another copy.
- When some covers are different in certain countries so you don’t get the main one which also happens to look better than all the other varieties.
- Basically just books.
- God damn them.