The Teacher's Bride, Amish of Birch Creek Series by Kathleen Fuller and published by Zondervan.
Christian, quiet and dedicated to learning, is focused on putting a rambunctious school into order. He's also determined to check off another task on his list: finding a wife. When he suffers an accident that puts him out of commission for a few weeks, Ruby steps in. Her teaching style and personality clash with his, and he wonders if all his hard work will be undone. Ruby thinks Christian is stuffy and decides to inject some fun into teaching the students. However, Christian can't keep his nose out of her business - both personal and professional. Relieved to be free of his overbearing hovering when her tenure ends, she's shocked when he makes her an unexpected offer, one that would solve several of her problems.