Great book: "What Happy People Know" by Dan Baker.
It's really impressive how well this ties in with the DB philosophy. The book discusses the science of happiness, and the personal decisions we make that decide whether we acheive it or not. It's not about marriage, per se, but I think we all understand the value happiness brings to M. I am only about half way through it (started it last night), but I recommend it wholeheartedly.
“No problem can be solved from the same level of consciousness that created it. ” – Albert Einstein