My next SF album from 1970 is American Beauty by
the Grateful Dead.
The Dead's two studio albums from 1970, American Beauty and Workingman's Dead, are their two best albums and their only studio offerings that casual fans need to own. They're both organic, and song-based, and completely antithetical to any preconceived stereotypes of what you think the Grateful Dead sound like (unless you learned about them from 70s and 80s FM radio)!
I like both albums, and had them on a double-length cassette for awhile, but if forced to choose I'd say that American Beauty is the Dead's masterwork. It has most of their best known songs ("Friend Of The Devil", "Sugar Magnolia","Truckin'"), a couple of stellar contributions from Phil Lesh ("Box Of Rain") and Pigpen McKernan ("Operator").
AB also has my favorite Grateful Dead song ("Ripple"), which I discovered via this performance from the Dead Ahead concert film.
After watching this film in high school, I picked up the Dead Reckoning acoustic live album and two 1970 albums which put me on the golden road to limited devotion.
I rediscovered this album a few months ago when the Bye Bye Blackbirds started covering "Till The Morning Comes", and since then, I've picked up the bonus reissues of American Beauty and Workingman's Dead and downloaded a bunch of Reckoning live tracks from emusic. But those three albums are the limit of my Dead devotion circa 2010. And I never inhaled!