Mutants: On Genetic Variety and the Human Body by Armand Marie Leroi
It's not a textbook, it's a narrative on various genetic disorders, the genetic code, some history of discoveries, etc... .
Here's the cover of it:
http://images.booksamillion.com/cove...0142004820.jpg
Although now, it's back to reading Fundementals of Human Anatomy and Physiology.. 1100+ page book (another 1000+ page book on the bookshelf)...