The paper itself is white but not very thick; my Tombow waterbased markers bled through to the other side and they're nowhere near as strong as alcohol markers. Like I said the single-sided book would be best, unless you prefer to scan and print images on thicker paper to colour. Each fairy house & door in this book is worthy of a frame, they're all so charming. There's lots of thick linework but the images still manage to appear dainty and quaint, which can be difficult to achieve with bold strokes.
Here's my finished fairy house- how I'd love to live there!