warp that makes a book splay open
Refers to a physical defect in a book's binding or cover that causes it to open by itself or not stay closed. Often used in book-collecting or book-repair contexts.
This paperback has a warp that makes it splay open as soon as you let go.
To fix a book that splays open, it's good to put a weight on it and leave it for a while.
Compound of 開き (hiraki, 'opening', from 開く hiraku) and 癖 (kuse, 'habit, tendency').