Dorothy L. Sayers left this
Peter Wimsey -
Harriet Vane novel unfinished in 1936 or so; unfortunately Jill Paton Walsh completed it in the late-90s. Sayers meant it to be an examination of the marriages of 3 couples (against the backdrop of a
murder); the finished product tries to be that, but has cringe-making passages that are surely Paton Walsh's contribution. If it had to be published at all, it should've been in the form of Sayers' incomplete fragment rather than this bad "
collaboration".