I'm currently reading The Heritage of Heinlein: A Critical Reading of the Fiction, by Thomas D. Clareson and Joe Sanders. I'll be reviewing this for The New York Review of Science Fiction.
Clareson and Sanders (mainly Sanders, since Clareson's contribution was some early chapters of the book that he drafted before his death in 1993) have produced a clear, careful, often insightful, and comprehensive discussion of Robert A. Heinlein's entire oeuvre of novels and short fiction.
In fact, reading this book has inspired me to go back and reread (or in a small number of cases, read for the first time) all of Heinlein's novels. We'll see how many I get through, and I expect to review some of them here - starting soon.
Heinlein has a strong claim to have been the most important science fiction writer of the twentieth century. If there is an SF writer who clearly surpasses him in importance, it is H.G. Wells, but Well's best and most innovative work was published in the 1890s. (Jules Verne was another great innovator, of course, but his most important books were published in the 1860s and 1870s; he died in 1905).
Obviously Heinlein has a few twentieth-century rivals - Arthur C. Clarke, to name just one - and some individual SF novels by more mainstream authors are more important than any single book by Heinlein. Think of Brave New World by Aldous Huxley, Nineteen Eighty-Four by George Orwell, and perhaps some of the works of Margaret Atwood, such as The Handmaid's Tale. Nonetheless, Heinlein's fiction was innovative, varied, often superbly crafted, and enormously influential.
It is, moreover, often undervalued by academic scholars and critics... for whatever reason. For example, there is no chapter on Heinlein in Blackwell's reference work A Companion to Science Fiction (ed. David Seed, 2005), even though there are chapters on H.G. Wells, Isaac Asimov, John Wyndham, Philip K. Dick, Samuel R. Delany, Ursula Le Guin, Gwyneth Jones, Arthur C. Clarke, and Greg Egan (I mean no disrespect to any of these fine writers - indeed, I wrote the chapter on Egan, and elsewhere I've written in depth on Delany). Nor is there a chapter on, say, Stranger in a Strange Land among the ten chapters on individual books.
As I've previously announced, I have a contract with the academic publisher Springer to write a book that will be (in brief) about science fiction and moral philosophy. This will involve much research that I expect to be enjoyable, in the form of immersing/re-immersing myself in much classic SF. There will be updates here as that book proceeds.