An interesting exercise is to group Crichton's novels by type in combination with some of his other works, which reveals an intriguing (rough) pattern regarding time of publication. Perhaps the correlation would be even tighter if we factored in the time of conception and/or the beginning of their writing. Something to look into...

MEDICAL DRAMAS - late 1960s and 1970s

1968                          1970                        1974                           1978

              

CAUTIONARY TALES (Technothrillers) - 1970s

 1969                           1972                           1973 

        

 Space exploration           Mind control                 AI    

1973                         1980                            1981

         

   Surveillance & privacy    Genetic engineering   Cosmetic surgery

   

HISTORICAL NOVELS  - mid 1970s to early 1980s

Four novels by Michael Crichton feature historical events. Pirate Latitudes and Dragon Teeth are among the novels that have been published posthumously as they were found among his unpublished materials, but there is evidence that they were written in the 1970s or early 1980s, like the previous two:

1974                        1975                      1976                  early 1980s 

                                 

American West 1886      London 1855    Volga-Bulgaria 10th century    Jamaica 1665       

SCIENCE FICTION - mid 1980 to 1990s

Michael Cricthon turned to popular sci-fi themes towards the 1980s, taking up the idea for Sphere he had conceived 20 years earlier, followed by Jurassic Park and its sequel and finally time-travel:

1984                        1987                             1990/1995                             1999

         

        Robots               Extraterrestials                Dinosaurs                 Time-travel

 

NOVELS ON CORPORATE CONTEXT - early 1990s

In the 1990s Michael Crichton turned to exploration of the corporate worlds. As always, with the (mis)use of technology as a backdrop, these novels center around cover-ups and corruption in big companies:

1992                                 1994                                 1996

                   

Video surveillance                   Virtual Reality                    Flight technology

NATURAL DISASTERS  - late 1990s

The only work of this type is the screenplay for Twister. I wonder if Eruption was also begun by Michael Crichton around this time...

1996                        ?

      

CONTROVERSIAL SCIENCE - early 2000s

His last three novels focused on cutting-edge research topics that had become controversial due to their societal impact:

 2002                        2004                       2006

 

Nanotechnology          Climate change         Gene patentig

Crichton's early novels under pseudonym do not seem to have a specific type other than being thrillers he wrote to make a living during his years at medical school, as he acknowledged several times. In my view this applies to all except A Case of Need, which is very much more in line with his later style and fits into the pattern presented here. It makes sense that it is the only one that was republished under his real name during his lifetime (The John Lange novels were republished under "Michael Crichton writing as..." in 2013).

The only novel missing here is MICRO. Given Crichton's consistent pattern with the type of works, we could speculate that it was begun during his sci-fi epoch. This is something to be checked, as well as whether his short stories fit this classification. One separate type of work some of the latter could be grouped into, together with his Insight screenplays and Playboy articles, is that of Psychology and interpersonal relationships. Work in progress...