The Monk by Matthew Gregory Lewis popped into my head immediately when I read the question. Written in ten weeks in 1796 by a not-yet 20 year old, The Monk may be evidence that Lewis was FREAKING INSANE. Ten weeks? He wrote this is ten weeks when he was 19??? That's freaking nuts.
Lewis made quite the splash with this novel as it was dirty, dirty, dirty. The notoriety of the novel transferred to Lewis who was known as "Monk" Lewis, the poor man. Lewis was complained of as "a reckless defiler of the public mind" and a man who "devoted the first fruits of his mind to the propagation of evil". He was also called a genius.
Sexually explicit and quite blasphemous, The Monk was a favorite read of the infamous Marquis de Sade. Of course, the general public was quite the fan as well; "They had been told that the book was horrible, blasphemous, and lewd, and they rushed to put their morality to the test". Who wouldn't?
The Monk is deliciously scandalous, and I think this sensationalism and shock value are, in part, the reasons it survived the years. Also, the plot is rather complex, in that intellectually challenging but overall satisfying kind of way; although it must be admitted that the narrative's complexity may be better described as absurdity, but in a super-fun, loving-it kind of way (he wrote it in ten weeks remember). I certainly hope the novel is treasured 100 years from now.
As for the last question, my brain is screaming that no, the book would not be well received if written now. First and foremost, its treatment of women is deplorable. Any woman in the novel who attempts to follow her dreams is sensationally, and violently, denied her success. Unless written with an obvious intent to highlight the horror of this misogyny, a book written today, I like to think, would be harshly criticized.*
Another indicator that this book would not work if written today is the heavy focus on "the Church". Much of this story is a criticism of religion, and while religion is certainly under scrutiny today, our religious practices have so drastically changed as to make these censures not quite apropos. Our ideologic construct of monks and nuns and the such not is practically nil, so stories centered on these characters are a bit difficult to relate to - at least in the same way readers back in the 18th century would have related to them.
Ultimately though, this is a fantastic read, a guilty pleasure of the classics, that I highly recommend.
*Of course, I believe we should criticize the novel - and harshly - for this misogyny despite the time period it was written; however, while I would generally dismiss with disgust a contemporary novel written with such a poor view of women, I quite strongly believe that works must be judged according to era-specific ideology, and as such I make allowances.