Update README.md

README.md

@@ -1,4 +1,6 @@
 ---
 license: apache-2.0
 ---
-467 Project Gutenberg books, mostly of older provenance (author died pre-1914), chapterized by Chapter Captor (https://arxiv.org/abs/2011.04163), then requiring the number of chapters is correct and the assigned numbers are sequential starting at 1.
+467 Project Gutenberg books, mostly of older provenance (author died pre-1914), chapterized by Chapter Captor (https://arxiv.org/abs/2011.04163), then requiring the number of chapters is correct and the assigned numbers are sequential starting at 1.
+
+Keys are "chapter_number", "text", "title", and "metadata{"id"}""  The id is the Gutenberg book number.  Title is often not present.