Paul Pedley. The invisible Web. London: Aslib-IMI, 2001. ISBN 0-85142-461-9 £13.99 (£11.00 for Aslib members)

The 'invisible' Web is that part of the Web that a) does not get indexed by the search engines because the pages are generated from data bases 'on-the-fly', and b) is at lower levels on a site, when the search engines may be indexing only the top 10%, 15% or 20% of the site. The danger is that one may believe that such pages are not worth looking at, but the author cites evidence to the effect that the quality of 'invisible' Web pages can be considerably higher than the indexed part.

This little book, in Aslib's series of 'Know How Guides', identifies the nature of the 'invisible' Web and what it contains, how to find information in this part of the Web, and how to make 'invisible' pages visible. There is also a directory of search tools that are adapted to search the 'invisible' Web and a 'Selective list of invisible Web resources.' Both of these lists are very useful but I would not describe some of the resources listed as 'invisible'; rather, they appear to be sites through which normally 'invisible' resources might be discovered, such as Bookfinder.com for rare and second-hand books, Stepstone for jobs, and Encyclopedia Britannica . This is a relatively minor quibble, however, and, in general, the list is useful.

The penultimate chapter gives four fairly typical reference enquiries (for example, 'What are the most popular travel destinations for UK holiday makers?) and shows how these were answered by using the idea of the 'invisible' Web. (I almost missed one of these questions because, unlike the rest, it did not begin with the word 'Question:'.

Finally, there is a good list of references, a glossary, and a good index. Any Web searcher would do well to read this little book and it would be worth checking the author's own Web site to see if there is further information. Updating in the area is always a problem as Pedley points out in the conclusion and it is likely that some of the resources checked in the early part of 2001, as these were, will have disappeared, moved, changed their orientation, or whatever by the time you read this review. With the Web being reckoned to be growing at the rate of about 7,000,000 pages a day and with a half-life of two years keeping pace is a job for the searcher, rather than for the author, who can only give a start to the process.

Henry Fisher
Wolverhampton