Joni and Ken share their untold love story

They vowed to stay together "for better" and "for worse" and they certainly had their fair share of "worse", but 30 years on Joni Eareckson Tada and her husband Ken want to share with others the secret to a contented marriage.

Joni married Ken, a football coach, in 1982 and while he thought he knew what he was getting into, he soon became overwhelmed with the never-ending responsibility of caring for Joni, a quadriplegic from the age of 17 after a tragic diving accident.

She was in chronic pain, he was suffering from severe depression. After the initial romance wore off, the reality of "in sickness and in health" drove them further apart rather than closer together.

Later, when she was diagnosed with breast cancer, Joni wondered if it might be the final wedge in their relationship.

It was around this time, however, that Ken experienced a spiritual transformation of his own, embracing a part of his heritage he had long misunderstood, and they figured out the secret to not just surviving, but thriving as a couple.

Now they are compelled to share that with others.

"Although Ken and I probably don't meet all the family-counseling criteria for 'a happy marriage,' this I know for sure," Joni writes, "Home is wherever we are together.

"It's why this book was written. For many people . . . I think all of our lives are spent looking for and wanting to go home. But what if it were as close as the hand of your spouse? That would make for a contented and complete marriage."

Their new book, "Joni & Ken: An Untold Love Story" is co-written with Larry Libby and shares with honesty, the highs and lows of their 30-year marriage and how, as each looked to God to find strength to carry on, they also found themselves drawing closer, in God's perfect love triangle.

"Joni & Ken: An Untold Love Story" is out from Zondervan in physical and digital format on 2 April.