But it requires active, exclusive use of time to go to a library, loan out a book, and bring it back (and additional time to return it), whereas I can do whatever while the book is en route.
That is true. However according to my experience you don't need to spend much time in the library itself if you know what you're looking for (you can always stay for the atmosphere). What takes time is going to and from the library. The value of this time obviously depends on a lot of parameters: is the library close to your route to/from some other place, are you currently very busy, do you enjoy city walks/bike-rides, etc.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.