{{ $scratch := newScratch }}
{{ template "recurse" (dict "Scratch" $scratch "Sections" .) }}
{{ define "recurse" }}
  {{ range .Sections }}
    {{ if and .Content (not .Params.BookHidden) }}
      {{ $.Scratch.Add "BookPages" (slice .) }}
    {{ end }}
    {{ if .IsSection }}
      {{ template "recurse" (dict "Scratch" $.Scratch "Sections" .Pages) }}
    {{ end }}
  {{ end }}
{{ end }}

{{ return $scratch.Get "BookPages" }}