Main genre: Science Fiction, Horror, Children, Fiction
Main audience: while he wrote some children's stories, I'd say his main audience is Young Adult on
Main books: Stranger in a Strange Land, The Puppet Masters, Starship Troopers, Have Space Suit Will Travel, Time Enough for Love, The Star Beast -- these are just a few of the books on Goodreads list of books -- and he wrote more than those, including numerous short stories. (He had 32 novels, 59 short stories, and 16 collections published.)
Short summary of the author: Robert Heinlein had the academic and practical knowledge to write science fiction and was very inventive in his works. "In the first chapter of the novel Space Cadet he anticipated the cell-phone, 35 years before Motorola invented the technology." "He also anticipated mechanical computer aided design with "Drafting Dan" and described a modern version of a waterbed in his novel The Door into Summer, though he never patented or built one." wikipedia page
This man wrote a couple of the most scary books I've ever read. One of them was The Puppet Masters and the other is The Unpleasant Profession of Jonathan Hoag. I think that what was so scary about them is that they both contain truth about 'what is' -- and the consequences of 'what is'. The Puppet Masters has been made into a movie two times. The first one, with Donald Sutherland, is frightening and yet it is not half as frightening as the book! I encountered his books while working in the school library and read everything they had. I loved reading about "intelligent, fiercely independent female characters" and also very much enjoyed his books because he wrote about feelings and life. (I also read Isimov but while he has very good books, for me he is too much up-in-his-head.) Heinlein invented some words - grok ( click ), waldo ( click ), speculative fiction ( click ), as well as popularizing TANSTAAFL ( click ) and other words and expressions. I find it very grand that he invented the word 'grok' because it was needed in the story and the words in English which refer to that way of knowing (to know something from your heart and gut and not from ego/intellect) had fallen out of common usage. The closest word which is used now in the English language is the Scottish word 'ken' (to know, or understand). Oddly, when looking up the word 'ken' online, none of the English words to define it work! A person has to go to another language, such as Spanish or German, to obtain more of an accurate definition. For example, with Spanish - compare the difference of conocer and saber. [To express knowledge or ignorance of a fact or information about something, use “saber.” To say that one is or is not acquainted with a person, a place, or an object, use conocer. ( click ) .] Heinlein bypassed all of that and invented grok and within the context and content of his book, people acquired that word resonance again.
As for popularity -- his books have acquired a range from those who feel he is the best science fiction author to ever walk on the earth to those who would burn every book he wrote and dance upon the ashes.
Goodreads has this writeup:
Robert Anson Heinlein was an American novelist and science fiction writer. Often called "the dean of science fiction writers", he is one of the most popular, influential, and controversial authors of "hard science fiction".
He set a high standard for science and engineering plausibility and helped to raise the genre's standards of literary quality. He was the first SF writer to break into mainstream, general magazines such as The Saturday Evening Post, in the late 1940s. He was also among the first authors of bestselling, novel-length science fiction in the modern, mass-market era.
