I created a website with a lot of content and no commercial intentions.
At the start I had many separate pages with small amounts of
information and multiple levels of navigation and Google was ranking
the site content in a most satisfying way but the complexity of the
navigation and many separate pages meant that a lot of content, was
being neglected by visitors.

I combined the content into fewer larger pages that use bookmarks
(...htm#bookmark) to get the visitor to specific information on the
larger pages. This encourages more browsing on the site and more
content is viewed. The change improved the visitors experience but
ruined the Google rankings, even though the identical information
remained on the site.

To try to repair the damage I've added all the previous small pages to
the site contents list hoping Google will find, index, and treat them
as before, restoring the previous rankings the site enjoyed. The site
has one navigation system for google and another for visitors.

Apparently, if you put a 500 page book online, you can improve the
rankings by dividing it into several thousand separate files with small
sections of the book on each. The individual files will be ranked
higher by Google than a single file with the entire book.

My issue might be resolved if Google treated text between bookmarks on
a page the same as it treats text in separate files, otherwise content
that should remain as single files, single pages, like books, becomes
impossibly fragmented and the only way to search is with
google--perhaps what they have in mind.

Google doesn't search the web, Google is the web.