The DC Universe Legacies book is an interesting concept. I'm always a sucker for a good concise retelling of the history of DC Comics. Having said that, after reading DCU Legacies #1 of the series, I came away thinking two things:
I was less than impressed with that first issue.
I couldn't think of any reason why I wouldn't wait to read this all together in a trade.
Having said that DC Comics recently released the cover to Issue #7, and it is really sweet. The Half Doomsday - Half Bane background with Superman and Batman in the foreground is brilliant in my mind.