Requirements:
git clone https://github.com/anoved/ReadingListReader.git
brew install coreutuils
sudo brew link coreutils
cd ReadingListReader
chmod +x readinglistreader.py
Command to run:
./readinglistreader.py --fields url | gsort -R | head -n 1 | xargs open
This will not, unfortunately, remove it from your Reading List.
For more information on ReadingListReader, a Python library and tools for working with Safari's Reading List, visit the project's README.