My simple bookdown project build files

_bookdown.yaml

book_filename: "test_bookdown_yaml"
delete_merged_file: true
language:
  ui:
    chapter_name: "Chapter "
rmd_files: ["index.Rmd"] #index
#, "01-introduction.Rmd","03-methods.Rmd", "02-data_input.Rmd", "03-methods_analysis.Rmd","04-results-obsers.Rmd","04-results-process.Rmd", "04-simulation1.Rmd","05-discussion.Rmd"]
#, "03-methods-process-models.Rmd"],"04-results-April2020.Rmd"
always_allow_html: true

_output.yaml

bookdown::gitbook:
  css: style.css
  config:
    toc:
      before: |
        <li><a href="./">Book title.</a></li>
      after: |
        <li><a href="https://github.com/username/repo" target="blank">Published with bookdown</a></li>
    edit: https://github.com/username/repo/docs/edit/master/%s
    download: ["pdf", "epub", "mobi", "docx"]
    link-citations: yes
bookdown::pdf_book:
  #includes:
    #in_header: preamble.tex
  latex_engine: xelatex
  citation_package: natbib
bookdown::epub_book: default
bookdown::word_document2:
  #reference_docx: ms.docx
  fig_caption: yes
  toc: yes
bookdown::html_document2:
  theme: yeti
  fig_caption: yes
  toc: yes
  toc_float: true
  code_folding: hide
  df_print: paged
  number_sections: false

IndexNewBook.Rmd

---
title: "Book title"
site: bookdown::bookdown_site
output: bookdown::gitbook
#github-repo: username/repo
subtitle: "Sub info"
# bibliography: ["references.bib", "book.bib"]
---

# Summary {#summary}

A great summary and setup here using bookdown