I can no longer compare it to versions 1.x, but all I can say is, Marvin's Library in the most recent 2.x versions instantly strikes me as ugly, employing the hideous iOS 7 pseudo-aesthetics of blinding whitespace.
I try to avoid opening Marvin's Library now because it's really awful to look at. The right-hand slide-out panel is not optimal, either (gives you the feeling of "cramped space").
The worst thing that has recently happened is the "progress" row of dots being removed, replaced with technocratic percentage numbers.
I just hate that. I have nothing against the percentage numbers, but
in addition to the progress row, not
instead of it.
So, now we have neither a visual progress row, nor a visual book length indicator, and we now only have hideous iOS 7-like blinding whitespace instead, leaving most of the iPad screen unused. All in all, a failed Library design, in my opinion.
For the associated GitHub issue, see
https://github.com/kguil/Marvin-Roadmap/issues/32