My present computer has ample RAM. I therefore created the whole manual as a single multi-chapter document (approx. 14Mb) and find that using the index, then going to the page in the manual is almost as fast as having a HTML file. Of course, it takes time to create this single document. And of course you then use a copy.
http://www.davidpilling.info/cd/DavidPilling/Documentation/Pdf/manual.pdf
There are two ways to create a single document. The easy way is by copying chapters into a single document, the hard way is by Alt-dragging/drop first the text and then all pictures from the separate chapters to the single document. I advise the latter especially if you want to do testing on the (copy of the) manual.
-- David Pilling email: david@xxxxxxxxxxxxxxxxxxx web: http://www.davidpilling.net post: David Pilling P.O. Box 22 Thornton Cleveleys Blackpool. FY5 1LR UK fax: +44(0)870-0520-941