This could predate your actual TBR or bookshelf but it's usually something outside your wheelhouse. Sometimes it's just the idea of a book. I could be a better person if I read this. I would be cool if I read this. I would learn so much. I could totally be into poetry. Everyone has read this except for me - it's basically required reading for existing, so do I even exist if I haven't read it?? Etc, etc. Make your actual self and ideal self duke it out.