Yes, it's a classic, belonging to a different age... And showing once again why I stay away from them. What pretentious, convoluted, drawn out, pointless prose. What overly theatrical speech and behaviors. What obvious plots that all, as in the hero at first and the villains later, never suspect and unerringly fall for. For that matter, what dastardly, irredeemable villains, and what a hero whose only flaw at first is being too good, too noble, thinking too well of others. And what an almost complete lack of information about how it was all achieved, the time in between the escape and the plan actually being set in motion. That would have been much more interesting, but its place is taken by a sizable portion during which the book seems to just drift off.
Maybe those with a keen interest in the Parisian high society of the period would enjoy the style and all the exhaustive descriptions that overshadow and cast aside everything else. Those with a similar interest in that of Rome may even enjoy the part I see as taking all the book's flaws to an even higher level. Harder to see who might enjoy the talks between Valentine and Maximilian but, in general, some of those who know why the book was written may be willing to pardon the author for a lot, including for simply wanting to show off his interests and preferences. I, however, don't.
I recognize some objective literary value, can also appreciate that the hero loses that initial naivety and gains the necessary ruthlessness but also falls into the clutches of pride and vanity, no longer being flawless, and can find some enjoyable parts, and that the book as a whole does seem to get better after the "nocturnal interview", but don't care to look away even from something like the lack of explanations, or at least translations, for the occasional Latin sayings, much less all the major flaws making me lose track of these relatively rare relevant parts among all the filler. Or, to put it bluntly, the bullshit ending.

Note: Think I read this before, likely in my early teens, but I'm not sure how well I understood it back then if so and not much seemed familiar now. The fact that it would have been translated in Romanian then and it was translated in English now might have also prevented some mental links from forming but, either way, it's pretty much as if I read it the first time.