When it becomes a chore. When the stupidity surpasses my ability to tolerate stupidity. When the writing is poor enough to detract from the story.

You have no obligation to finish a book. There are too many good books out there to waste time on one you don't like!

(Also you're completely right, 7 1/2 Deaths... was such a brilliant book but his follow up had that second album problem. Hopefully the third will be great)

Life is too short to read books you're not going to enjoy, OP.

My biggest enemy is boredom - I have to be engaged to keep reading. Although the last two books I've abandoned were for other reasons. One because of a graphic animal-abuse scene that I couldn't make it through and one that turned into a Christian novel half-way through. None of the reviews mentioned it, but apparently the author found god and released a new, improved printing featuring extra Jesus. Blech.

I have a Kobo ereader at my bedside table and read almost every night in order to fall asleep, so when I dread picking that up I know I either have to double down and finish the book or drop it. So far it has only happened once in recent years. That time it was Salvation by Peter F Hamilton, a hefty chunk of a book. If it’s a novella I generally try to read more often just to finish it.

I generally give up after 100 pages or so if it hasn't caught my interest by then.

Life is too short to slog through a book just because other people liked it.

I try to do it before I even touch it. 😊

The best way to do that is to select your next reads by relying on your own previous reading (that gets easier as you read more), or on the opinions or recommendations of people that know you very well or have very similar tastes.

I haven't abandoned a single book in years. The few times I was tempted to throw something aside, it was because I was misled by hype (and comparisons that seemed promising but didn't deliver), or - most commonly - because someone gave it to me as a present.

If I find myself skimming pages and pages. I know I've lost interest in the book.