I've had this and Thom's earlier book (Megalithic Sites in Britain) from the same publisher, for very many years. They've lived next to each other on the same shelf in my home. The earlier book is still in excellent "as new" condition with white paper etc. Unfortunately my copy of Megalithic Lunar Observatories is suffering from quite distinct yellowing of the pages, and I'm beginning to wonder just how long before the pages crumble away to dust! I'd recommend any would be purchaser to enquire about this aspect before purchasing. It does seem as though a different quality of paper was used.
For anyone interested in studying stone circles, alignments etc. this book continues from Thom's earlier work, Megalithic Sites in Britain, and deals with many of the Scottish sites in more detail. An excellent, if at times quite difficult, read.