The title implies that the author will offer some answer to the question posed therein -- but he doesn't appear to do anything of the sort. The literary excerpts, reproductions of paintings, etc. are worthy and of interest to anyone with any sense of esthetics, letters, or history, but the message of the collection seems to be simply that we should put things in perspective because we'll all die anyway. This is a fine enough theme for a collection, I suppose, but it doesn't stand up to what the author purports to share with us -- namely, a reason that choosing one thing over another has no impact on our lives.
The fact is that our decisions do have an impact on our lives, no matter how unimportant our lives may be in context. Our impending deaths -- and the grand, rushing current of human history in which any one life is a single droplet -- is to my mind another matter entirely and does not bear on the issue which is supposedly at hand.