One of my favourite courses among those offered freely to the public at the University of Edinburgh is Astrobiology and the Search for Extraterrestrial Life by Prof Charles Cockell. It is a free course that is split into weekly sessions focusing on the basics of astrobiology. The course has no pre-requisites making this a perfect course for beginners.
The course consists of approximately 5 weeks of study for which the recommended time of study is around 4 hours a week. For the full syllabus head here.
Astrobiology: A Brief Introduction by Kevin W. Plaxco and Michael Gross
A good basic introduction to Astrobiology.
‘A Short Introduction to Astrobiology’ by David Catling and ‘Life in the Universe: A Beginners Guide’ by Lewis Dartnell are also very good sources.
Planets and Life: The Emerging Science of Astrobiology by W. Sullivan and J. Baross. Cambridge University Press
A little pricey, but quite comprehensive survey of astrobiology
An Introduction to Astrobiology by D. A. Rothery, I. Gilmour and M.A. Sephton. Open University
A good summary of many topics in astrobiology.
Impossible Extinction: Natural Catastrophes and the Supremacy of the Microbial Worldby C S Cockell
A book about the remarkable tenacity of microbes on the Earth
An Introduction to the Earth-Life System by CS Cockell, R Corfield, N. Edwards, N. Harris.
A text book about the co-evolution of life and planet Earth
Space on Earth: Saving Our World by Seeking Others by C S Cockell
A book about the links between the Earth’s environment and the exploration of space.