Superman is arguably one of the three most recognizable fictional characters in the entire world. He is known all over America, Europe, Africa, Asia, etc. He is the ultimate immigrant and embodiment of the best human qualities. Several books have been written explaining the origin and appeal of this incredible character during his long career (one of the most recent, and very recommendable: Our Hero, by Van Zee).
He is usually depicted as invulnerable. However, he has no defense against a terrible force that has plagued fictional characters always: Bad Editors and Poor Writers.
This title (Sacrifice) was an attempt to deconstruct the superman mythos, and give us a broken character that needed to be fixed during the next several years (hence given DC editors a nice steady income).
The storyline was presented back in 2005 when plans to refresh the entire DC-Comics line of characters were underway. At that point in time, a second tier character in need of yet again a new injection of vitality was chosen to help breaking the superman mythos: wonder-woman (a well known character in North America, and a few other countries, but basically unknown in most of the world).
The idea was to present a renewed wonder-woman that could appeal to male readers, given her a stamina almost as impressive as superman's. In addition, an emphasis was given to the few weapons this character relies upon (tiara, lasso, etc.) indispensables to ensuring her survival in a fight against the most powerful being in the DC-Universe.
This approach produced a short term interest in the second tier character, however, over the last few years the increased power levels have been a drawback for wonder-woman comics sales. After the original appeal of having a female crime fighter willing to kill if appropriate, during 2007-2010 her comic book sales were steadily decreasing to the point of selling less copies than practically unknown characters (such as Booster Gold). A new change was needed, and in mid-2010 wonder-woman was depowered (yet again), to more human levels (roughly half the strength of Superman), and a new costume was given to her. The objective is to make her close to Superman strength (70-80% of his), and focusing her adventures to the realm of magic and mythos.
Fortunately, the editors at DC comics seem to have learned that in order for their fictional universe to work, Superman needs to be the epitome of greatness. He cannot be portrayed as a supporting character (as he is in this collection) in any storyline of relative importance. This is especially true if these books have any hope to be sold outside the US, where Superman is still considered the Greatest Hero of Them All !!!