diff --git a/rules/rules.mk b/rules/rules.mk
index dbe1cfc9..e345b278 100644
--- a/rules/rules.mk
+++ b/rules/rules.mk
@@ -530,12 +530,17 @@ SILEFLAGS += $(call use_luas,$(LUAINCLUDES))
 
 preprocess_macros = $(CASILEDIR)/casile.m4 $(M4MACROS) $(PROJECTMACRO) $(TARGETMACROS_$1)
 
-$(BUILDDIR)/%-$(_processed).md: %.md $$(wildcard $(PROJECT)*.md $$*-$(_chapters)/*.md) $$(call preprocess_macros,$$*) | $(BUILDDIR) figures
+$(BUILDDIR)/%-$(_processed).md: %.md $$(shell $(_ENV) list_related_files.zsh mds $$*) $$(call preprocess_macros,$$*) | $(BUILDDIR) figures
 	if $(HIGHLIGHT_DIFF) && $(if $(PARENT),true,false); then
 		export FILTERS="$(filter %.m4,$^)"
 		branch2criticmark.zsh $(PARENT) $<
-	else
+	elif $(RG) -qw loadchapters $<; then
+		# For books using the old M4 macros to load chapters, only process the first dependency
 		$(M4) $(filter %.m4,$^) $<
+	else
+		# For books using the new related files finder, load all md files except the first dependency
+		# Add blank lines between files so headers aren't eaten, c.f. https://unix.stackexchange.com/a/628651/1925
+		$(M4) $(filter %.m4,$^) =($(SED) -s -e '$${p;g;}' $(filter %.md,$(wordlist 2,9999,$^)))
 	fi |
 		renumber_footnotes.pl |
 		$(and $(HEAD),head -n$(HEAD) |) \
diff --git a/scripts/import.zsh.in b/scripts/import.zsh.in
index 25751d24..916efcd0 100644
--- a/scripts/import.zsh.in
+++ b/scripts/import.zsh.in
@@ -41,4 +41,4 @@ import_${format} $bookid $input
 untrack $input
 commit "Import $format source as $bookid"
 
-"$CASILEDIR/scripts/split_chapters.zsh" 2 $bookid
+"$CASILEDIR/scripts/split_chapters.zsh" 3 $bookid
diff --git a/scripts/list_related_files.zsh.in b/scripts/list_related_files.zsh.in
index 7f680431..0098e39b 100644
--- a/scripts/list_related_files.zsh.in
+++ b/scripts/list_related_files.zsh.in
@@ -2,24 +2,34 @@
 set -e
 
 cmd=$1
-base=${2/.md}
+bookid=${2/.md}
 
-value() {
-  echo $@
-  exit 0
+function value () {
+    echo $@
+    exit 0
 }
 
 case $cmd in
-  meta)
-    value $base.yml
-    ;;
+    meta)
+        value $bookid.yml
+        ;;
+    mds)
+        alias git="@GIT@"
+        # Separate commands to set our own sort priority
+        git ls-files "$PROJECT.md" ||:
+        git ls-files "$PROJECT-*.md" ||:
+        git ls-files "$bookid.md" ||:
+        git ls-files "$bookid-**.md" ||:
+        exit 0
+        ;;
   srcid)
-    $0 meta $2 | read meta
-    if [[ -f $meta ]] && yq -e 'has("source")' $meta >/dev/null; then
-      yq -r '[.source[] | select(.type == "bookid")][0].text' $meta | read bookid
-      value $bookid
-    fi
-    ;;
+      alias yq="@YQ@"
+      $0 meta $2 | read meta
+      if [[ -f $meta ]] && yq -e 'has("source")' $meta >/dev/null; then
+          yq -r '[.source[] | select(.type == "bookid")][0].text' $meta | read bookid
+          value $bookid
+      fi
+      ;;
 esac
 
 exit 1
diff --git a/scripts/normalize_files.zsh.in b/scripts/normalize_files.zsh.in
index c6856b53..0f79dcb8 100644
--- a/scripts/normalize_files.zsh.in
+++ b/scripts/normalize_files.zsh.in
@@ -19,18 +19,14 @@ pandoc_args=(
 # TODO: do we need turkish filename hacks back?
 # $(SED) -n '/^#/{s/ı/i/g;p}' |
 
-# TODO: finish and use related files finder?
-# $CASILEDIR/scripts/list_related_files.zsh $bookid |
-
-git ls-files "$bookid-*/*.md" |
+$CASILEDIR/scripts/list_related_files.zsh mds $bookid |
 	xargs rg --files-without-match loadchapters.zsh |
 	while read file; do
 		basename $file | IFS='[-.]' read no _
 		dirname $file | read dir
 		rg -m1 '^#' $file | pandoc ${pandoc_args[@]} | read identifier
+		[[ $identifier == nil ]] && continue
 		git mv -k "$file" "$dir/$no-$identifier.md"
 	done
 
-echo done
-
 commit "Normalize $bookid filenames based on heading ids"
diff --git a/scripts/split_chapters.zsh.in b/scripts/split_chapters.zsh.in
index 3ab4c36b..903da5d4 100644
--- a/scripts/split_chapters.zsh.in
+++ b/scripts/split_chapters.zsh.in
@@ -4,7 +4,6 @@ set -e
 source "$CASILEDIR/scripts/functions.zsh"
 
 alias pandoc="@PANDOC@"
-alias sponge="@SPONGE@"
 alias sed="@SED@"
 alias mkdir="@MKDIR_P@"
 
@@ -14,7 +13,7 @@ test -n $splitlevels
 bookid=$2
 test -n $bookid
 
-# TODO: actually support --top-level=part where parts are another level of splits
+# TODO: restore support for top level being chapters instead of parts
 part_no=0
 chapter_no=0
 section_no=0
@@ -34,27 +33,29 @@ while read -r line; do
 	[[ $line =~ "^\[\^1\]: .*" ]] && break
 
 	# Check for headers
-	if [[ $line =~ '^\\part\{.*\}$' ]]; then
-		of=$bookid.md
-	elif [[ $line =~ "^#+ .*" ]]; then
-		if [[ $line =~ "^# " ]]; then
+	if [[ $line =~ "^#+ .*" ]] || [[ $line =~ '^\\part\{.*\}$' ]]; then
+		if [[ $line =~ '^\\part\{.*\}$' ]] && [[ $splitlevels -ge 1 ]]; then
+			chapter_no=0
+			section_no=0
+			let part_no=$part_no+1
+			dir=${bookid}-parts
+			mkdir $dir
+			of=$dir/$(printf %03d $part_no).md
+		elif [[ $line =~ "^# " ]] && [[ $splitlevels -ge 2 ]]; then
 			section_no=0
 			[[ $line =~ ".*unnumbered.*" ]] || let chapter_no=$chapter_no+1
-			dir=${bookid}-chapters
+			dir=${bookid}-parts/$(printf %03d $part_no)-chapters
 			mkdir $dir
 			of=$dir/$(printf %03d $chapter_no).md
-			files+=($of)
-			>> $bookid.md <<< "esyscmd([[loadchapters.zsh \"$of\"]])"$'\n'
-		elif [[ $line =~ "^## " ]] && [[ $splitlevels -le 2 ]] then
+		elif [[ $line =~ "^## " ]] && [[ $splitlevels -ge 3 ]]; then
 			[[ $line =~ ".*unnumbered.*" ]] || let section_no=$section_no+1
-			dir=${bookid}-chapters/$(printf %03d $chapter_no)-sections/
+			dir=${bookid}-parts/$(printf %03d $part_no)-chapters/$(printf %03d $chapter_no)-sections
 			mkdir $dir
 			of=$dir/$(printf %03d $section_no).md
-			files+=($of)
-			>> $bookid.md <<< "esyscmd([[loadchapters.zsh \"$of\"]])"$'\n'
 		elif [[ $splitlevels -ge 3 ]] then
 			flunk 'Unsupported 3 level split'
 		fi
+		files+=($of)
 	fi
 
 	>> $of <<< "$line"
diff --git a/upgrade-markdown.sed b/upgrade-markdown.sed
index a61da3ae..c003447f 100644
--- a/upgrade-markdown.sed
+++ b/upgrade-markdown.sed
@@ -1,3 +1,4 @@
 s#zsh -c 'for f in *#loadchapters.zsh "#
 s#; do cat \$f; echo; done'#"#
 s#\\lang\([a-z]\+\){\([^}]\+\)}#[\2]{lang="\1"}#g
+/loadchapters.zsh /d