I like the simple complexity of this book cover. The layers of the earth contrasting with the simple leaf acting as the frame for the title of the book.
My inspiration for the September calendar page came from a combination of this and the following book cover design. I liked the idea of using simple lines (though mine aren't quite as simple) for the structure of the tree, but was inspired by the rough rock path of the 2nd image to expand that idea into larger leave spread out over the entire page for the calendar days.
I like the geometric shapes of this one, with the contrasting black against red, highlighted with the gold. My son argued that the red (on my version on the October calendar page) looked awkward. He was expecting the red to highlight a specific part of the calendar, like the days of the week end. I decided to leave it like I had it, similar to this image, for the viewer to ponder over.