If you want to understand the Beatles music, get to know Geoff Emerick.
Geoff began working as their sound engineer when he was still a teenager and knows details about how they recorded their music that the Beatles themselves probably don't know!
I've read a bunch of interviews with him and watched some great videos too, where he takes us through many of The Beatles classic recordings. Here's one to start with:
Sound engineer Geoff Emerick remembers recording The Beatles Sgt Pepper's album