How bout Garage Inc? Have mixed feelings about doing a load of covers. Some I like, but a double album of covers? I dunno.
It was mainly for hardcore fans so they could get their hands on Garage Days/Garage Days Revisited. Which people were ending up having to import, so Metallica wanted all that available to the fans. I also think they had an interesting choice in new covers, if anything, those choices really showed how much the band had changed over the years.
Their cover of Astronomy is the best one of the new ones IMO.