I'll start by saying that I enjoyed their quirky combinations of music and moving image quite a bit, but that was tempered by a feeling that the music seems to be fatally trapped between worlds. Their output straddles an eclectic fence of indie rock, minimalist classical, and electronic collage music; and while such combinations are not new, I feel that this throws their proportions out of balance for the aesthetic they're going for... or at least I think they're going for. That confusion might itself be the problem for me. But in any case, their music often strikes me as too long for the indie rock stuff, but too short for the collage/minimalist style.
I think they fit better into the latter, and I don't think it's a put-down to say that they're not really destined for much airplay beyond college radio. I would love to see a bit more development in their music. I think they've really got a spark, but often it gets snuffed by the confines of pop paradigms.
One side note... I noticed that a number of images were re-used in their videos. This kind of made the videos feel cheap, and I don't just mean the cost. Low-budget is fine (preferable?) for the indie crowd, but low personal investment is unforgiveable.
Anyway, here are two examples of music by the Books. One I think works, and one I think doesn't quite.
This one works great: