I tried to read this in my youth but gave up; however after recently discovering Mann's superlative 'Buddenbrooks', thought I would give it another go.
From the point of view of narrative, Mann sustained my interest throughout. The account of young Hans Castorp, on the brink of a career, who goes to pay a brief visit to a consumptive cousin in a Swiss sanatorium but ends up staying so much longer; the description of life in an institution - albeit a luxurious one; the treatment of the disease in the early years of the 20th century were of great interest. And as events take their toll, and we reach the seance scene - and indeed the ending of the story - Mann's lovely writing brings tears to one's eyes.
However the narrative is interspersed with great sections of philosophical musings, as Hans becomes acquainted with two opposing mentors, Settembrini and Naphta, ('it was again impossible to distinguish which side was in the right, where God stood and where the Devil, where death and where life') whose lengthy and obscure harangues made this reader's heart sink, and felt like wading through porridge. I absolutely confess to only getting the drift of a small percentage of this, coming to identify with the character Ferge, "to whom all elevated thoughts were foreign."
Rating the novel is thus difficult, as I fully realise that loftier minds than mine have been able to appreciate Mann's work. And that the author himself, in his postscript, requests 'that it be read not once but twice' to get 'a deeper enjoyment.'
I shan't be re-reading it; I have to say that when I finally reached page 716 I shouted 'hurrah! I've done it!' It's lovely in parts but mighty heavy going.