Abbey Road is more or less The Beatles' final album1, and it contains some of the group's strongest work – especially George Harrison, who finally gets his day in the sun.
I'm not sure when I got my first copy of Abbey Road. Might have been high school, or it might have been the first release of The Beatles' catalog on CD. This was back in the dark, pre-Internet, ages when knowing exactly what the "official" Beatles releases were was non-trivial.
The vast majority of Abbey Road was in heavy rotation on the local classic rock stations all through my formative years, of course, but it's best appreciated in its entirety.