Didn't pick up the book
He’s talking about the Big Book of Alcoholics Anonymous which is a “bible” for the movement. It contains the twelve steps of the program, commentary on each step, personal anecdotes from AA members, and additional material designed to support and educate an AA member on their path to sobriety. At meetings, members will often quote the Big Book. Macklemore is saying that he ought to have picked up the book.
Read the Big Book of AA online here.
Of course, Step 2 of the AA program is “Came to believe that a Power greater than us could restore us to sanity.” As such many fans have come to believe that a second allusion in the line is the Good Book, the Holy Bible. There’s no question that he’s reading the Big Book, but it’s plausible, given the high-profile spiritual content in his songs, that Ben wanted the spiritual guidance of the Word of God, but couldn’t bring himself to breach the perceived distance between God and himself.
To help improve the meaning of these lyrics, visit "Starting Over" by Macklemore and Ryan Lewis (Ft. Ben Bridwell of Band of Horses & Macklemore) Lyrics and leave a comment on the lyrics box