Theindexer will want a feel, before they begin, for the concepts that willneed to be flagged, or taxonomized with subheadings. They mightskim the book – reading it in full but at a canter – before tackling itproperly with the software open. Or they may spend a while, as apreliminary, with the book’s introduction, paying attention to itschapter outline – if it has one – to gain a sense of what to look outfor. Often, having reached the end of the book, the indexer will returnto the first few chapters, going over them again now that they havegained a conceptual mapping of the work as a whole.
It's no wonder that Mortimer J. Adler was able to write such a deep analysis of reading in How to Read a Book after having spent so much time indexing the ideas behind The Great Books of the Western World.
Indexing requires a solid inspectional read at minimum, but will often go deeper into contexts which require at least some analytical reading. To produce the Syntopicon, one must go even further into analytical reading to provide the proper indexing of ideas so that they may be sub-categorized and used for deeper analysis for things such as comparison and contrast of those ideas.
Photo of Richard Macksey's Library by Will Kirk