I highly recommend You're Not Going Crazy...You're Just Waking Up! The Five Stages of the Soul Transformation Process by Michael Mirdad. It's a very succinct (90 pages) and accessible primer on both crisis (the hard way) and transition (the easy way). He doesn't refer to just mid-life, but does say we all have one major one in our lifetimes, which, if we don't complete, will show up at other times. It confirms a lot of what we've read here about both the MLC experience and what we've lived within our own LBS crises.
It refers also to the tunnel, the light, the dark night of the soul, and many other metaphors we use daily. It doesn't make light of infidelity, heartbreak, the hellish nature of the whole thing, and the abuse a person in crisis may inflict on others. At the same time, the crisis is not painted as an evil trauma - it can be a very rewarding experience if we accept the change that comes and allow it to improve the rest of our lives.
The five stages are:
1. Dismantling
2. Emptiness
3. Disorientation
4. Rebuilding
5. A New Life.
He says 1-3 can all be considered Dismantling and 4-5 Rebuilding, with a gap in between that we must take the leap of faith to reach if we don't want to stay stuck. He emphasizes that our lives will never be the same after this, but even if we liked our prior life, that's ok - we can rebuild an even better one with what we learn.
It would no doubt appeal across a broad spectrum of spiritual belief - it does quote Jesus, as well as Mother Teresa, The Beatles, Jung, Buddhist writings, and Duran Duran - so there's as much a lighthearted take as there is scripture. I would consider it about as New Age as this website is, for anyone sensitive to that. It cites A Course in Miracles quite a bit, which I know very little about but will now be researching more (even if it's some sort of New Age-y cult or something, I don't feel that association has darkened the info in this book for me).
So if you're seeking an afternoon read that would provide even more insight and confirmation into this process, as well as maybe provide a few exercises for achieving more from your LBS experience (there is a simple one for each stage), I would highly recommend this little book.