Indexing, the value of

Indexes are often regarded as insignificant elements of non-fiction books, to the extent that corner-cutting publishers often ask authors to compile them themselves or omit them altogether. And yet, as Sam Leith argued on 30th March (National Indexing Day), a good index can be an enormous help to readers in desperate search of information or passages relevant to their specific topic and requires a skillful indexer rather than a computer algorithm. I'd also second Leith's comment that the indexes in Alan Partridge's two books I, Partridge and Nomad are as amusing as the main text.

(Thanks to Lisa for the link.)