To be honest, I haven't been able to suggest one. Mainly because most of what is out there seems a bit cheesy.
My daughter and her new husband came across a book by Jim and Cathy Burns called "Closer." And I think it's terrific. It's the first book I have seen that has the right combination of Biblical truth, discussion starters, and practical application.
If you're looking for something like this for yourself (or a great wedding gift that will have greater value and purpose to a young couple than another serving spoon), give "Closer" a try. You can get it pretty cheap at ChristianBook.com. And if you have come across another couple's devotion book that you have enjoyed, please share it here. I'd love to know about it.