I found it tough but satisfying. I thought that there were enough non-theme clues and crossing letters to get a glimpse of the theme, which I did have to google for the full quotation. Last one in was 14d, which I didn't know, but was fairly clued. My favourite clue was 4a: Playwright turned inside out by elements of former problem with Iceland (6) It didn't help that for a while I had 5d as HAVERING, and assumed that the Icelandic problem involved ASH...