Books differ so much in size and difficulty that this is a rather meaningless metric. Even on the fiction side the differences in size are huge (typically 100

Books differ so much in size and difficulty that this is a rather meaningless metric. Even on the fiction side the differences in size are huge (typically 100 pages to 1300 pages) and the ease of reading differs as well. On the non fiction side the differences in reading speed can be 100x depending on difficulty and familiarity with the material. For example, I'd consider the workload of one semester of my university program equivalent to about three medium sized books, which amounts to two months per book, without a fulltime job on the side.