One can make a very good argument that this is where power metal began. Before Legion, before Fates Warning and Queensryche, and definitely before Helloween.
Yes, you are probably familiar with this album. After all, Metallica covered half of it. That said, the original is definitely worth finding. Actually, what is really worth getting is the Half Moon Records "best of" which is remastered, and has the best sounding versions of some of these songs. But, not others. For that, there is only the original. Beware of the crappy Century Media pressing, try to get the original Happy Face vinyl if possible.
The album is marked by some awesome guitar soloing by Brian Tatler - very tastefully done, as in not wankery. The best examples are on "Am I Evil" which is total Richie Blackmore worship, and also "Sucking My Love" and "The Prince", which is more a Glenn Tipton sounding deal. Also, the songs themselves are very catchy - think almost of early Fates Warning, and you can have a good idea of this particular species of power metal.
The only kinda throwaway song is "Sweet and Innocent", which isn't as much a throwaway as much as it doesn't belong after "Am I Evil". Other than that, the album is just about flawless. Nice guitars, and also some pretty nice vocals by Sean Harris.
Easily one of the best albums of the NWOBHM - highly recommended.