Diversity in writing

I have just finished By Nightfall by Michael Cunningham, who you all (I hope) know as the author of The Hours. Now The Hours is one of my favourite novels, so when I found out that there was a new novel by him, I had to read it (I have somehow missed Specimen Days being published, probably because I was studying biology and only had eyes for fantasy, like most eco-nerds). I was expecting something great and moving and romantic, or at the very least, something set in a historical period with a woman as the protagonist.
Instead, I got a novel about a man in his forties, living in New York, and going through a massive mid-life crisis. Granted, he is an art dealer, so there is something romantic-artistic about the novel, but other than that, the only connection to The Hours is that there is a gay person in it (I won't tell you who it is, because that would be spoilering. Also, I just found out that the author is gay himself, which may explain something).
Don't get me wrong, By Nightfall is brilliantly written and very gripping, and I think it is quite an accurate depiction of current-day New York/society (I've never been to New York, but I hope to be able to tell you in a couple of months). I loved reading it, I will probably read it again (also because it is small and light, but still takes you a couple of days to get through it, so an ideal travel book). But it was just so very different from what I was expecting. So very different from the novel that I know.
This is something that I am still genuinely awe-struck by; authors who can produce a new book about every 5 years, and have all those novels be about completely different things, different periods, different people, even in a different genre. Everything I have ever written has similarities on some basic level and no matter how hard I try, they always somehow creep in. I wish I were able to somehow step out of that "history of writing" and do something completely different, and every NaNoWriMo I try, but it has somehow never happened.
With Ian McEwan (I will always get back to him when given the chance), you can see he has many different subjects and periods and characters, but there is always that thing that connects his novels, his style of writing, the little details, the things that make you go "ah, typically McEwan!" (although Solar is perhaps the exception to that rule, now that I think about it...). That is what it must be like to be a great writer; to be able to deal with a diversity of subjects, but still have readers recognise your style (or "voice", although that sounds very artsy-partsy). I think Michael Cunningham hasn't fully done that, because I did not recognise the same voice that told the story in The Hours, but I do admire his ability to deal with stories that are so very different. Granted, there are some great writers who stick to one area or field or subject and write brilliant books too (Jane Austen? Neil Gaiman?), but I have to admit I do prefer the first kind of author. Because with them, there are always new worlds, new societies, new ideas, new people to discover. So I can't wait for Michael Cunningham's next novel, although I am afraid I will have to wait for a couple more years!