It's set in 1776-1792, and was published in 1859. So for its first readers, the setting was only as long ago as the 1929-1945 period is for us: the descent into homicidal totalitarianism of a country which now generally behaves as a responsible neighbour.
Both Doctor Manette and Sydney Carton, the two most interesting characters in the book, have obvious, and sympathetically portrayed, mental health problems. The Doctor is a pretty clear case of what we would now call post-traumatic stress disorder. Carton thinks of himself as simply an alcoholic, but clearly has irrationally low self-esteem and probably depression. Today he would, one hopes, have access to drugs and therapy, though even in the eighteenth century he is more or less able to hold down a high-profile job (the stress of which probably doesn't help).
Madame Defarge, however, is not mentally ill, just vindictive.
Is there another Dickens book with both a memorable opening and a memorable ending?
There were a number of sentences involving Manette which I was tempted to post here as a "which Doctor Who novel is this from" quiz, because he too is almost always referred to as "the Doctor". (Added bonus for fans of the recent Paul McGann audios is that these passages tend to involve his daughter Lucie.)
The comic Cruncher family are the one part of the book that doesn't work so well for me. Dickens is often a bit annoying when he does the rude mechanical bit but normally he finds some humanising feature. (The characterisation in the book is generally thin even by usual Dickensian standards.)
To finish on a more appreciative note, Dickens does social horror very well, and effectively links the social injustice of ancien régime France to inequality in contemporary England, and also even more effectively links the brutality of aristos and revolutionaries to the brutality of the British judicial system; it's not a past thing from a few decades ago, it's a hook for one of his best and most heartfelt class warfare arguments.
Anyway, it's brilliant, and I will not wait another 25 years before I read it again.