http://audrey.fmf.uni-lj.si/hott.html NOTE: my blog is being slashdotted by Hacker News. Please read this static version of the blog post while I resolve the issue. By Andrej Bauer, on June 20th, 2013 The HoTT book is finished! Since spring, and even before that, I have participated in a great collaborative effort on writing a book on Homotopy Type Theory. It is finally finished and ready for public consumption. You can get the book freely at <http://homotopytypetheory.org/book/>http://homotopytypetheory.org/book/. Mike Shulman has written <http://golem.ph.utexas.edu/category/2013/06/the_hott_book.html>about the contents of the book, so I am not going to repeat that here. Instead, I would like to comment on the socio-technological aspects of making the book, and in particular about what we learned from open-source community about collaborative research. We are a group of two dozen mathematicians who wrote a 600 page book in less than half a year. This is quite amazing, since mathematicians do not normally work together in large groups. In a small group they can get away with using obsolete technology, such as sending each other source LaTeX files by email, but with two dozen people even Dropbox or any other file synchronization system would have failed miserably. Luckily, many of us are computer scientists disguised as mathematicians, so we knew how to tackle the logistics. We used <http://git-scm.com/>git and <https://github.com/>github.com. In the beginning it took some convincing and getting used to, although it was not too bad. In the end the repository served not only as an archive for our files, but also as a central hub for planning and discussions. For several months I checked github more often than email and Facbook. Github was my Facebook (without the cute kittens). If you do not know about tools like git but you write scientific papers (or you create any kind of digital content) you really, really should learn about <https://en.wikipedia.org/wiki/Revision_control>revision control systems. Even as a sole author of a paper you will profit from learning how to use one, not to mention that you can make <https://vimeo.com/68761218>pretty videos of how you wrote your paper. ... --- co-chair http://ocjug.org/