There are lots of good geology books, but I recommend these ones - all up-to-date, well-illustrated and readable, without too much jargon! For field guides with detailed descriptions of different areas of Scotland, check the publications of the Edinburgh Geological Society and Geology Society of Glasgow.
Hidden Landscape, Richard Fortey, 1993 - now updated, 2010.
Geology and Landscapes of Scotland, Con Gillen,
Landscape fashioned by geology series, Scottish
Natural Heritage/British Geological Survey.
Edinburgh Rock: The Geology of Lothian, by Euan Clarkson and Brian Upton. Published in 2006, the book is written by two of the geologists who taught me at Edinburgh University. The enthusiasm I remember from their teaching bubbles from the pages. Euan Clarkson and Brian Upton have made a great team, bringing together their expertise in different areas to provide a comprehensive description. The book is written for non-specialists, but given the nature of the story and the amount of detail included, it is inevitable that there is a fair amount of geological terminology to be wrestled with. Read it with a geological dictionary to hand! Dunedin, 1903765394.
By the same authors, Death of an Ocean: a geological borders ballad (2009) continues the theme and explores the fascinating and under appreciated story of the Southern Uplands. Dunedin, ISBN 9781906716028.
Set in Stone, by Alan McKirdy 2015. A great little book, exploring the big stories of Scotland's geology for a non-specialist audience. Birlinn, ISBN 9781780271514.
Land of Mountain and Flood, Alan McKirdy, John Gordon and Roger Crofts, 2007. A big book in all senses! A grand overview of the geology and landscapes of Scotland, with chapters on why geology is important in all our lives, Scotland's journey and the future on different time scales. Places to visit, and plenty, big, beautiful photos to inspire you. Birlinn, ISBN 1 84158 357 X.
Volcanoes and the Making of Scotland (2nd edition),
Brian Upton, 2015