This is an interesting idea, and one that I've never come across before. PB&J refers to two books that are better when read together. I found the concept here at the Barnes & Nobles blog.
Sure there are books that are better read together. Like, all of the Harry Potter books. And The Hobbit with the Lord of The Rings trilogy. But what about books that aren't written together?
Fascinating! I guess that's what higher-level college courses do, throwing books into a curriculum that are, indeed, better when read together. That's the beauty of higher studies in English--it's enlightening to read Marx before diving into the commodity culture of Our Mutual Friend.
But this concept did inspire me to tell you, oh vast interweb of lit lovers, to read Dickens' Oliver Twist right before diving into Sarah Waters' Fingersmith. It's my absolute favorite pairing and the novels I used for my grad school application paper.