My work friend's marriage was in trouble years ago. She knows how it feels to be a LBS. She's been a great support for me.
I am currently reading "This Is Not The Story You Think It Is" by Laura Munson, which is a first-hand account of dealing with her husband's MLC, and I see "the script" that J is following in her husband's behavior.
I also have "His Midlife Crisis" and "Male Midlife Crisis" by the Conways to read. They're a little more heavy into the Christian focus than I am, but the books are very highly recommended for looks into the male MLC perspective and the perspective of the MLC spouse.