I'm not the person you're asking, but my answers would be "not really" and "no".
When or if to give up on a book is a personal decision. Personally I try to allow an author 20% of the page count if the book is well written, less if it isn't. I wish I'd applied that rule to Seveneves, but I didn't because it had been so heavily recommended. By the time I'd finished it I actually felt angry for having my time wasted.
My opinion of Stephenson is that he is smart guy and an able writer (particularly of non fiction), but also that he is an undisciplined writer.
I think the problems started with Cryptonomicon. The book is great, but it’s very apparent the final act of the book is just missing. He clearly ran out of time and just slapped something together and it was hugely well received (and with good reason, there’s lots to like). But the success of a book that frankly got away from him made him near untouchable. So yeah, undisciplined is what happens next.
The last part is so different from the rest, that it may as well be an unauthorised sequel written by a different author with a different personality, because they didn't like how the previous bits ended.
In my experience, how you like reading a book is hugely influenced by your state of mind and situation when you read it. You might love a book this month but have found it boring six months ago. It's just something you need to bear in mind (I loved Seveneves).
When or if to give up on a book is a personal decision. Personally I try to allow an author 20% of the page count if the book is well written, less if it isn't. I wish I'd applied that rule to Seveneves, but I didn't because it had been so heavily recommended. By the time I'd finished it I actually felt angry for having my time wasted.
My opinion of Stephenson is that he is smart guy and an able writer (particularly of non fiction), but also that he is an undisciplined writer.