Added special syntax for unnumbered part headers: # (PART\*). Numbered parts should be written after # (PART) as before (thanks, @brooksambrose, http://stackoverflow.com/q/43688902/559676).
The gitbook output format also supports abstract in YAML now (thanks, @maxheld83, #311).
For the gitbook output format, the downloads option in config supports rmd now (e.g. download: ["pdf", "epub", "rmd"]) if the edit link has been specified and is a link to Github (thanks, @coatless, #330).
You can set the global R option bookdown.post.latex via options() to be a function to post-process the LaTeX output of the pdf_book format; see ?bookdown::pdf_book for details (thanks, @nicksolomon, #373).
The HTML output file is not moved to the output directory when split_by = 'none' in bookdown::gitbook or bookdown::html_book (http://stackoverflow.com/q/40976073/559676).
The YAML option includes: before_body works correctly for gitbook output now (thanks, @benmarwick, #267).
Theorem environments are not defined for LaTeX output unless a theorem block is present (thanks, @JeffreyRacine, #291).
For remark and proof blocks, the chunk option name did not work correctly for non-LaTeX output (thanks, @ugroempi, #347).
Some text references do not work for HTML and Word output (thanks, @ugroempi, #363).
The option chapter_name in _bookdown.yml does not work when it is specified as a function (thanks, @tzerk, 0c05c3828be).
External assets such as fonts/css files should never be wiped when rendering a book to HTML (thanks, @nicholaelaw, #398).
The daemon argument was removed from serve_book(), but you can still pass it to servr::httw() via the ... argument.
Added a small space (padding) to the right of section numbers in gitbook output, so that the section numbers are better separated from the titles (thanks, @aronatkins, #367).
Added a Github button in the group of sharing buttons on the toolbar. By default, this button is not displayed. You have to set github: yes under sharing in the gitbook configurations (https://bookdown.org/yihui/bookdown/html.html) and specify your Github repo using the top-level option github-repo in the YAML metadata of index.Rmd, e.g. github-repo: rstudio/bookdown.
The appendix heading will be preserved in bookdown::html_document2 output, e.g. if you have # (APPENDIX) Appendix {-} in your document, you will see the heading Appendix in the output. Previously it was removed.
Parts in HTML output are also be numbered using roman numerals like LaTeX/PDF output.
Wrong part titles were inserted to the table of contents of PDF output (thanks, @florisvdh, #243).
Cross-references for appendices in html_document2 output did not work (thanks, @florisvdh, #245).
Part titles were not correctly processed when they were longer than 20 characters in PDF output (thanks, @florisvdh, #246).
Added arguemnts toc_unnumberred, toc_appendix, toc_bib, and quote_footer to pdf_book().
Added support for cross-referencing equations in multi-page HTML output and EPUB; see https://bookdown.org/yihui/bookdown/ for the syntax (thanks, @deleeuw, #85).
Rmd files can live in subdirectories if you use the Merge-and-Knit approach (the default), and they will be found if the configuration option rmd_subdir is true in _bookdown.yml (thanks, @leobuchignani, #205).
force_knit argument of render_book() was removed (to avoid confusion when switching output formats).The merged R Markdown file will not be deleted if rendering failed so you can debug with this file (http://stackoverflow.com/q/38883222/559676).
The configurations edit: text and chapter_name have been moved from the top-level options to the sub-options of language: ui in _bookdown.yml. See https://bookdown.org/yihui/bookdown/internationalization.html
Figures are not correctly numbered in Word output using the bookdown::word_document2() format (thanks, @byzheng, #158).
For the "Knit and Merge" approach (new_session: yes in _bookdown.yml), certain parts like figures may not show up when switching from one output format to another (e.g. from HTML to LaTeX).
The rmd_files option in _bookdown.yml does not work when it is a list of html and latex options (thanks, @ismayc, #177).
Math expressions does not appear in the table of contents when the output format is gitbook (thanks, @philomonk, #204).
Footnotes of multiple paragraphs are not displayed on the current page (thanks, @axitdn, #234).
The output format pdf_document2() also works with articles now when an R Markdown document contains bookdown-specific headers, such as parts or appendix headers (http://stackoverflow.com/q/40529798/559676).