When Academic Press first suggested that we might write a book about Lucid, we readily agreed. Producing a book would be relatively easy (we
thought); we could simply collect a number of existing papers and reports,
add a few editorial comments, and that would be that. Once that was
taken care of, we could then move on to some more ambitious project.
However, when we went back and reread the papers and reports, we
realised that out initial plan was unworkable. Lucid was (and still is) a
very new development; nevertheless, it had already evolved so much that
the various papers we proposed to include had become incompatible.
Some of the changes were of a detailed or technical nature, but on the
whole they reflected a radical shift in the underlying motivation.