Space.com published a great list of books about space, from classics to modern, from science to fiction. I marked for immediate exploration Michio Kaku ‘Hyperspace’ (1994). The only concern I have is that it’s so dated. Another ia a seminal Mars colonization classics: Robert Zubrin’s ‘A Case For Mars’ (1996), also a bit older, but I don’t think it will be dated in terms of content. I’ve read that what Zubrin imagined in this work became a staple for Mars colonization vision.