This 1987 book has long been out of print. Oxford published only 1000 copies. There remains interest in its material, as issues of visibility remain central to many areas, particularly sensor networks, wireless networks, security and surveillance, and architectural design. When I noticed that used-book sellers were offering it on Amazon for as much as $1847 (and at one point, EUR 2151,90 at abebooks.com!), I sought to obtain the copyright from Oxford, which they graciously returned to me. (Thanks to Stefan Langerman for suggesting this, and to Erik Demaine for suggesting scanning it.) So now I can offer the book free to anyone on the web. (But please note I retain the copyright, and all copyright laws apply.) I had it scanned by Kirtas Technologies. They did a nice job but accidentally missed pages xii & xiii of the Table of Contents. So I scanned those two pages myself and added it to the full book PDF. The book is linked below: both the full book, and each chapter individually in case you want just a portion of it. The PDF files are searchable in any PDF viewer that supports text searching, except for the two ToC pages xii & xiii (which were scanned to jpeg).
See also my new book, Art Gallery Visibility Theorems: An Introduction, 2027 (in press).
