I have taken months to read this brick of a book - I have wondered whether going for the edited version would have been a better bet. I haven't read anything by this author before, but dialogue, characterisation, and plot pacing would not seem to be strong points of this book. It does have some interesting ideas (communication of concepts being more powerful than materials, the importance of trying to understand a thing before passing judgement on it, etc.) but these are telegraphed, and not subtle in a way which would be expected of an "allegorical" work.
Overall it is hard to review the book without comment on the story itself, which seems to have been the only reason for the book's contentiousness. Whilst the basic evolution of the "stranger" of the title from innocent to messiah is nothing new, the actual change happens quickly, almost between chapters, and at first is hard to swallow. There a few digs at contemporary establishments, but nothing more interesting.
The author is plainly an "ideas" author who ought to leave the wordsmithing to someone more accomplished (the work of Neil Gaiman I would place in a similar bracket - intriguing but barely readable). His views come over through most of the story - in that respect only it is similar to "brave new world" which would have worked better as an essay of opinion rather than sci-fi.
The biggest trouble is that the author's views have not aged well (most memorable point in case is where a female character comes to the realisation that rape "is the woman's fault, nine times out of ten" which made me slightly fearful about what recommendations amazon might suggest when I logged in again...) and his female characters in general are one-dimensional, mostly there to please or else be gawped at by the male characters. The dialogue would often seem more suited to pulp fiction (the genre, not the film) with early sections sounding oddly reminiscent of raymond chandler novels and later sections are plagued by throat-clearing (one central character seems to start each section of speech "Mmmm..." from about halfway through and more and more characters seem to do it back to him).
So, did I like it? Not really. It was an effort to finish, which good writing never is. Whilst I'm sure the fans of this book would be aghast and suggest I re-read to "grok to fullness", I can't be bothered. But I'm happy with, and take full responsibility for that decision. Which seems to be Heinlein's point all along.