“!” → tells Jupyter notebook to pass the remaining line to bash shell
[ -e /content ] → is the command in bash to check if a file or directory exists and returns true or false. So, here we’re checking if a directory called content exists at the path /content (/ is the root directory and content would be right under it if it exists)
&& → it means “If the last command returned True, run the next command.” So we just checked whether a directory /content exists or not. If it exists we’ll move on to running the command that comes after “&&” since the output of [ -e /content] would be “true”
pip install -Uqq fastbook → install fastbook package and Upgraded it (-U) if it already exists. -qq means be very very quiet?