try

scrape.sh

@@ -0,0 +1,39 @@
+#! /bin/bash
+
+main() (
+   set -ueo pipefail
+
+   if [ ! -f ./raw.md ]; then
+      wget -q -O ./raw.md https://raw.githubusercontent.com/ZachGoldberg/Startup-CTO-Handbook/main/StartupCTOHandbook.md
+   fi
+
+   rm ./src/*
+
+   printf "# Summary\n\n" > ./src/SUMMARY.md
+
+   cat ./raw.md \
+   | (
+      n=0
+      while read -r line; do
+         n=$((n+1))
+         depth="$(echo "$line" | grep -o '^##*')"
+         (
+            echo n=$n
+            echo line="$line"
+            echo depth=$depth
+         ) >&2
+         if ((n>20)); then
+            break
+         fi
+      done
+   )
+
+   mdbook build
+)
+
+if [ "$0" == "$BASH_SOURCE" ]; then
+   main "$@"
+   ret=$?
+   echo ret=$? >&2
+   exit $ret
+fi