"Are 'best' and 'favorite' the same thing? If someone asked you 'What’s the best book you ever read?' would the answer be the same as for 'What’s your favorite?' "And I guess I found it interesting mainly because I can't imagine being able to come up with a single "favorite" or a single "best" book. If you asked me to name a favorite, we'd be here for hours.
Also, what's meant by best? Best plot? Best writing? Most valuable lessons taught? I can certainly recognize that many of my favorite books are not the most well-written books or the most morally uplifting -- in fact, many of them are really kinda trashy. But I still love 'em.
While the "best book I ever read" would, I suppose, necessarily have to be a favorite, my favorite books are many and varied, and they do seem to change over time. OK, that's clear as mud, right? I guess my answer would be that to me, best and favorite are pretty much the same thing where books are concerned, but impossible to name.