Mrs. Miracle by Debbie Macomber

Also a motion picture from the Hallmark Channel, this is a fan favorite from #1 New York Times bestselling author Debbie Macomber. 

They call her Mrs. Miracle…

Seth Webster's heart never healed after he lost his adored wife. Now, with Christmas approaching, wild twin boys to raise alone, a home in chaos, and the latest in a long line of exasperated housekeepers quitting in disgust, Seth needs more than help to keep his family together...he needs a miracle.

And then one arrives on his doorstep. Her name is Mrs. Merkle, but the kids call her "Mrs. Miracle"—and from the moment the warm, knowing, and very patient nanny appears, everything is different. Her sassy spirit is infectious, and it gives Seth the courage to approach Reba, a beautiful travel agent who's been hurt and betrayed, and is afraid to ever love again. Through the magic of faith—and with a little help from a children's Christmas pageant and a lot of encouragement from Mrs. Miracle—Seth and Reba might just be able to find a Christmas miracle of their very own: true love.