Excellent introduction to astronomy

Openstax.org is an initiative of Rice University that provides free educational materials to students world-wide.  In January 2020 Openstax published a web version of their textbook – Astronomy. This text provides an excellent introduction to many aspects of astronomy, from the fundamental science to galaxies, quasar, black holes and beyond.  This is an excellent resource for anyone interested in learning more about astronomy. Get web access to the book here.