Colouring books for adults have become very popular recently. If you are a reader as well as a colourer, you might be interested in this article listing 11 colouring books based on literature: http://mentalfloss.com/article/88176/11-literature-themed-coloring-books?platform=hootsuite.
Besides the ones listed above, there are a few others that caught my attention:
Little Red Riding Hood: An Adult Coloring Book with Classic Fantasy Characters and Relaxing Country Scenes (Based on the Brothers Grimm Fairy Tales)
Pride & Prejudice: An Adult Coloring Book with Romantic Country Scenes, Historical English Women, and Vintage Floral Dresses (Inspired by the Best-Selling Novel by Jane Austen)
The Official Outlander Coloring Book
The Literary Romance Coloring Book
This last one I think might be the most fun. Perhaps “literature” is not the appropriate word to use for romance comics, but these types of comics are often introductions to more serious reading.