btrfs (pronounced as in the title) is the next gen linux file system (you can tell it is a file system because it ends in “fs” which means “File-related stuff.”
Valerie Aurora nee Henson gives us “….a behind-the-scenes look at the design and development of btrfs on many levels – technical, political, personal – and trace it from its origins at a workshop to its current position as Linus’s root file system …” here