It's easy to say you're a fan of Pink Floyd if all you've heard is The Wall and Dark Side Of The Moon. But the time-honored system for getting into the band is to start with Dark Side, work forward and then work backward. As you do that, make sure Atom Heart Mother 
is the last Floyd album you listen to.
Some fans have claimed rabid devotion to this one, and they are wrong. It's a little more cohesive than its predecessor Ummagumma but far behind the music the band would create the very next year. This is especially noticeable in the sidelong title track, a dead-end trip that Floyd would only travel twice (the second was the far superior "Echoes").
Seriously, "Atom Heart Mother" meanders for 23 minutes without really coming to a point. Instead of a cohesive piece, it's just a random quilt of occasional highlights (a jam! an orchestral buildup! a female choir that wails for 8 minutes!). Each element is stretched far too long, simply for the purpose of filling up one side of an album. The band has since disowned this piece, saying they had neither the time nor money to finish it properly. That's all you need to know.
Four songs make up the second side, three of them solo band pieces and the fourth a waste of space. "If" and "Fat Old Sun" are pleasant but unremarkable, feeling like homemade demos, while "Summer '68" is a little gem that's the best song here, a little tune carried by flourishing horns and notable Beach Boys-like harmonies in the chorus.
Things come to a close with a 12-minute "song" dedicated to a man named Alan eating breakfast. It's the guys jamming in between sounds of sizzling bacon. If you must hear it, skip to the final two minutes, then walk away. In no way is this appealing or meaningful.
Singer/bassist Roger Waters has since said you could not pay him a million pounds to play the title track, because he refuses to play anything that embarrasses him. If the songwriter doesn't even like the two songs he wrote, why should the listener bother?