- the use of inflexible hotmelt glue instead of flexible cold glue,
- the death of signatures in which paper is folded like in a booklet and sewn around in favour of perfect bindings in which the edge of each page is stuck with glue onto the spine, and
- lack of awareness of grain.
It is common to find hardbacks that lack signatures and are bound using hotmelt. They are even worse than cold glue paperbacks of signatures. Sometimes printers even get the grain wrong.
This is awful for functionality as well. Books cannot open flat without splitting the spine, and signatures can be rebound many times. Hyphen Press’s article is quite good, though incomplete.