Exactly, I keep my library on my reader so I can browse and read whenever. I tend to reread books several times (with gaps of several months between readings). I read *really, really* fast (finish a ~1000 page book in 3-4 hours) so rereading is the only way to keep myself occupied (else I would go broke in short order trying to buy enough books).
Just as a for-example, last time I reread David Weber's Safehold series (up to book 8) it took me two days with breaks to play computer games and go to work, and those books are far from short...
So yeah, capacity and management are actually really important to me
More customization sounds really nice, sorry amazon...