The 3 "big" Sabbath albums to many people are Sabbath Bloody Sabbath, Master of Reality and Paranoid. Personally, I think if you're gonna own 3 Black Sabbath albums only, get this, Volume 4 and Sabbath Bloody Sabbath. These three are absolute essentials, and this album is a fucking monster.
People who don't like Ozzy-era Sabbath should seriously still check this out, Ian Gillan is an awesome singer, the music is very good chunky heavy metal, great lead work too. The album has it's doomier moments like Disturbing the Priest and Zero The Hero which have really huge guitar riffs and a "big" sound, then there's catchy heavy metal with a bouncy tempo like Digital Bitch and Hot Line. One of my fave Sabbath ballads, Born Again, is on here too, and it's excellent.
The lead work is actually quite similar to Ritchie Blackmore's in places. Tony seems to throw in his whammy bar and a few licks Blackmore could have used. As well as Ian's yelling in places, there's a distinct Deep Purple vibe. But the rest of the music is just great heavy metal done the Sabbath way. Awesome guitar riffs.
So yeah, anyone who gave up on Sabbath after Ozzy or anyone who thinks all Black Sabbath albums sound like the ones with Ozzy need to give this a listen, because it's a fantastic album. The album cover is a little, well, shit but the music is absolutely amazing.
(metal-archives.com/reviews/Black_Sabbath/Born_Again/517/)