The earliest spiders didn't build webs, rather they used silk to line their burrows, then adding lines to detect when prey came near. The coming of a new, stronger type of silk then allowed the building of webs, as well as other uses, such as the possibility of floating through the air. The book looks at the difference between horizontal webs, vertical webs and cobwebs, and has a chapter discussing the visibility of spiders webs - do they use camouflage or can insects actually be attracted towards their web?
The authors clearly intend this book to be accessible by the non-specialist reader, but I felt that they weren't particularly successful in this regard. There seemed to be a lot of long words - I had to constantly remind myself of the difference between mesotheles, mygalomorphs and araneomorphs. On the other hand, if you can live with that, then you are likely to find plenty to interest you in this book.