Understanding Wood by Dr. R. Bruce Hoadley would be it. Dr. Hoadley covers the entire breadth of wood science and technology in one straightforward, easy-to-understand, and enjoyable-to-read volume. This is a coffee table book for wood nerds. Filled with excellent, colorful pictures, and simple diagrams and charts, this book makes wood science accessible to anyone. And even the seasoned veterans of woodworking and the wood industry will learn a lot more than expected by spending time in its pages.
And finally, the book about wood that anyone can read and love, is Eric Sloane's classic A Reverence for Wood. I found a copy of this book in a souvenir store back when I was in college and I've kept a copy at my fingertips ever since. Mr. Sloane's style was to write simple vignettes and to illustrate the topic with freehand line drawings. A Reverence for Wood is only 111 small pages long, but you or your loved one will read them many, many times, in those quiet hours of reflection between chores. His books, which include other titles such as Diary of an Early American Boy, American Barns and Covered Bridges, Our Vanishing Landscape, The Seasons of America Past, and A Museum of Early American Tools, are all excellent companions and very handy for reflecting on life "in the good old days". I wish someone would give me the whole Sloane collection for Christmas!