This "Wisdom Tree" was purportedly designed because "readers love to read serval [sic] books simultaneously," according to manufacturer Bookniture.
I initially deemed it silly, but after thinking about it I can't deny it offers some utility. Where I think it would be very handy is in a reference situation, when you're in the middle of a project and have several books you're going back-and-forth with. However, in order to hold, say, the IRC or "Human Dimensions & Interior Space" it would certainly have to be more robust. (It looks like 1/4" ply to me in the photos.)