One of the qualities of a good book is the presence of a quality Back-of-the-book index (BOB). This is an index that uses basic indexing elements which help to network similar concepts and nouns scattered in the text. This book has tried to examine some of these basic indexing elements; and the extent to which these elements have been used in various books published in Nigeria, with special reference to Natural Science texts. It also tried to determine the depth of indexing, the filing and arrangement patterns of the index entries and finally, if differences exist in the indexes of secondary school texts and those of tertiary/general Science books. This book will be useful to library and information science students, and may serve as a reference resource for lecturers, research fellows, authors and publishers.