README.adoc in asciidoctor-epub3-1.5.0.alpha.15 vs README.adoc in asciidoctor-epub3-1.5.0.alpha.16

@@ -1,8 +1,8 @@
 = {project-name}: A _native_ EPUB3 converter for AsciiDoc
 Dan Allen <https://github.com/mojavelinux[@mojavelinux]>; Sarah White <https://github.com/graphitefriction[@graphitefriction]>
-v1.5.0.alpha.15, 2020-03-11
+v1.5.0.alpha.16, 2020-04-26
 // Settings:
 :experimental:
 :idprefix:
 :idseparator: -
 :imagesdir: data/samples/images
@@ -138,10 +138,11 @@
 Therefore, the {project-name} converter “chunks” the AsciiDoc source document into multiple XHTML files to add to the EPUB3 archive.
 Like other converters, Asciidoctor EPUB3 handles this chunking task by automatically slicing up the XHTML output at predetermined heading levels.
 
 When `doctype` attribute is set to `book`, each top-level section will become a separate ebook "chapter" file.
 This includes preface, bibliography, appendix, etc.
+This behavior can be configured via `epub-chapter-level` document attribute.
 
 Otherwise, whole document is converted to a single ebook chapter.
 
 You may specify custom chapter filenames by assigning IDs to sections:
 
@@ -295,9 +296,16 @@
 The recommended practice is to identify the referenced resource by means of a string or number conforming to a formal identification system.
 
 |epub-properties
 |An optional override of the properties attribute for this document's item in the manifest.
 _Only applies to a chapter document._
+
+|epub-chapter-level
+|Specify the section level at which to split the EPUB into separate "chapter" files.
+This attribute only affects documents with `:doctype: book`.
+The default is to split into chapters at level-1 sections.
+This attribute only affects the internal composition of the EPUB, not the way chapters and sections are displayed to users.
+Some readers may be slow if the chapter files are too large, so for large documents with few level-1 headings, one might want to use a chapter level of 2 or 3.
 
 |series-name, series-volume, series-id
 |Populates the series statements (`belongs-to-collection`) in the package metadata.
 Volume is a number, ID probably a UUID that is constant for all volumes in the series.