For me, Abacab is a paradox.
I grew up listening to the 1970-1980 Genesis, so I was accustomed to the "mellow prog/pop, 12 strings, big chords" thing.
One day, I found a cassette my mum had bought, that was still packed (maybe for 25 years...).
It was Three Sides Live.
I was quite surprised (and I didn't like very much at first) by the edgy "rock" sound of the three first tracks.
So, I knew the live versions of Dodo and Abacab before the studio ones (because my mum didn't have any album post-Duke, and I didn't know why).
When I finally got Abacab on vinyl, I didn't like very much...
"What ? They cut out the final part of Abacab ? That was the best part, you fools !"
"No Reply At All ? Phil should have kept it for Face Value, it suits him more..."
"Me and Sarah Jane... Ah, finally, a Genesis sounding song."
"Keep It Dark... Another version of Abacab... oh, the chorus is nice actually..."
"Dodo... God, these synths sound awful"
"Who Dunnit... What... What... What the... Hol.. Sh..."
"Man on the Corner... Well, after the previous one, I can appreciate anything, at least it has some musical sense..."
"Like It or Not... Typical Rutherford song, I prefer Your Own Special Way, but it's fine".
"Another Record... Oh, the intro sounds promising... Uh, in fact, I was wrong... Wait, a synth harmonica, really guys ?"
So, it took me some time before appreciating it. Still, it's not my favourite album, but I understand the concept, why it has been made that way, and some songs reached a new level when played on stage (the title track, for example).
It is an important album for the band, they changed the way they were working, they got their own studio... It's the most controversial among fans, and even the band stopped promoting it after 1987.
It's why it's a paradox, essential in their evolution but rejected and forgotten in some way...