I've learnt that it's perfectly OK to put down a rubbish book; there is no great Cosmic Law saying I must finish every piece of trash I pick up - it's really liberating.
It's perfectly OK to put down any book! I have tossed aside so-called classics because I thought they were awful. And it's not the old-fashioned language turning my off as I've read Shakespeare and Lord of the Rings and a few others. But one book that was still describing the titular house over 50 pages in? Yeah, I'm done.