Do whatever feels right, suits you and your lifestyle...I personally have about a 100 unread books in my bookshelf, and read whenever I have the time and energy...like you, I like to focus on what I'm reading, so some days, I'll read 2 pages of each book (currently reading 3, technically 4) some days none, some days 10 or even more...as a result though, it takes me a looooong time to read a book (usually 2 or 3 months)

Would be too worried it would be something I already own or have already read and don't want to reread...also I get incredibly picky with books, wouldn't read just anything...would be a shame to get a book I'm not even remotely curious about🙈