For 2016 Author Robert McCrum has compiled a list of the 100 best non-fiction books. These are “key texts in English that have shaped our literary culture and made us who we are”, in the Anglo-American English language tradition, the list covers “essential works of philosophy, drama, history, science and popular culture”.

Number 11 is The Selfish Gene by Richard Dawkins. Some things to look at in this index:

• The introductory note explains that the index can be used to look up references in the bibliography as well as in the book, the numbers in brackets refer to the bibliography. So – acquired characteristics  23 (139). That could be useful.
• The introductory note also says that common terms are not indexed every time they appear, and so they shouldn’t, but only in special places such as where they are defined. For example the term ‘allele’ has only one page number and a reference to the bibliography, but occurs in several other sections of the book. I’d have to read a bit to see if that means there are too few page numbers in the index.
• Most of the terms are not plurals. It can be tricky sometimes to consider if a term should be singular or plural nouns in an index. The rule of thumb is if it can be counted it should be plural, but if you say ‘how much’ then it is singular. The index should be consistent and the indexer should be aware of the context of the words to decide if a singular form is more appropriate than a plural. The index is consistent, so for example the types of animal mentioned in this index are singular.

The book has a relatively short index, only 7 pages for over 300 pages of text. The publisher may have decided that this was not to be a reference book and the lightness of the index reflects that.