I struggled to finish this crossword.
It was hard from beginning to end (as it should be), but I felt that there was too much solver knowledge assumed. Essentially all the missing letters had to be discovered in order to get the theme, unless you were already familliar with the work and could make a guess at it. Not having any indicator for the (-1) down clues was pretty mean and, I think, an unnecessary complication, although I can see how a contrary view might be argued. Despite this, one can still marvel at the cleverness of the construction.
Overall, the puzzle was a slog rather than a challenging pleasure. I only persevered because I don't like to be beaten!
I hope there aren't too many like this in the pipeline.
Rant over!