Lindbergh (wife of famed aviator Charles Lindbergh, and mother of the baby who was famously kidnapped and murdered in the early 1930's), muses on the nature of marriage, motherhood, aging, and contentment in this classic collection of essays written while she vacationed on a Florida beach in the mid 1950's. Using seashells and other organic materials that tend to collect on beaches and in the cottages where visitors stay, she compares and contrasts the elements of nature with the elements of modern life, which in the United States, was changing quickly in the aftermath of World War II and the booming economic situation that followed. Lindbergh isn't necessarily critical of modern life, just aware of the speed with which it tends to move, especially when juxtaposed against the slow passing of peaceful days at the ocean. Sarah Ban Breathnach, author of the phenomenal 1996 best-seller Simple Abundance refers to Gift of the Sea often in her own work. Indeed, Gift of the Sea is sometimes credited with being the first book created in the genre of women's inspirational literature.
I also have read Simple Abundance many times. This was not the question that I posed ; but thank you for answering just the same.