I'm still not sure who LEGO Rock Band is for. I'm sure there's somebody out there that owns Rock Band 2, but doesn't want to admit he listens to metal songs, and has a couple kids that refuse to play anything without cartoony characters, and a mother in law who is so bad at rhythm games she needs them to practically play themselves. Plus this guy likes to spend full price for half a game. Lego Rock Band is perfect for you, dude.
Trying to tell you whether or not you should buy this game is complicated. Honestly it might require an extensive flowchart. I can tell you right off the bat that ...

Lizhard is a Hard Rock band from Italy. It all starts in a small town called Rescaldina near Milan, around 1995 when Luca “Ze” Moroni (bass) asks Ricky Lecchini (drums) to form a band called “Lego” (in a few years he decides to change the bandâ?™s name into Lizhard, a joke between the ex-singer’s name Liza and the genre they play). Beginning as a cover band, they play a lots of hard rock hits for many years during their live shows in northern Italy and Switzerland. Thanks to their born-out friendship transmitted during their power shows and the captivating voice of Luke Marsilio, the band is soon appreciated by the audience. So they decide to start writing their own music.