This book is like an ocean liner holed beneath the waterline at several points but with effective bulkheads. Although seriously flawed the leakage is contained and the ship stays afloat.
Perhaps the problem is the ship's construction was never completed. Thomas Mann was clacking away at the typewriter just before his death at the age of 80, and more surprising than the fact that the novel remained unfinished is the fact that the narrative voice is that of a smug young man, a charlatan who has decided to regale us with a glib account of his early career.
Because of the necessarily episodic nature of such a fly-by-night career, the story resolves itself into a series of loosely-connected episodes.This is definitely fortunate as some of the episodes are of incomparable brilliance while others are heavy going. In a story with more unity this would have the effect of sinking the whole ship, but compartmentalized as they are, we are able to enjoy Mann's purple passages without too much reference to the episodes that don't work.
The episodes where Felix evades military service and the whole section where he recounts his Parisian days as elevator boy, jewel thief, dishwasher, and popular waiter at a top hotel, were particularly effective, showing Mann's deft touch for entwining character, psychology, and manners.
After these bright spots, most readers will probably feel the last third of the novel, mainly set in Lisbon, is wasted. Here we have a lot of cosmic gobbledygook from Professor Kuckuck and the tedious courtship of the Professor's daughter, Zouzou, who never advances beyond an abstraction of a surly, spoilt young lady. There is still the occasional speck of gold to be panned here in these muddy lower reaches, but the river has by now lost most of its sparkle.