Last night at Congregation Beth Elohim in Park Slope, singer-songwriter Jeff Tweedy discussed his new book “World Within a Song” with journalist Amanda Petrusich. The book is a series of riffs on 50 songs that have meant something to the Wilco frontman over the course of his life, from the sublime to the silly. After the talk, which was earnest relatable and often funny, Tweedy took a few requests from audience members (all dudes of a certain age) and played a spare acoustic set in the soaring v