TerriBull- I make good use of my local library & "try before I buy". Like others have said, if a book doesn't really hold my interest I discard it & return it.
However, if the book in question is the library's Reading Group book, I do my best to work my way through it, as I feel that you can't have a reasoned discussion about a book you don't like without being able to say exactly what it is about it that you didn't like, can you - if you're still with me!?
I admit that if that happens,(a book by a motormad chap called Jeremy Clark-something springs to mind), I will skim or give up very quickly.
Waiting patiently
on a shelf for me to have another go at is Gormenghast.