TL;DR: 8/10. I like the book; it is a captivating story written in a fantastic style, which I completely fell in love with! There are a few weird moments in the second part of the book, but they can be perceived realistically, depending on your perspective.

TL;DR: 6.5/10. Great start, excellent adventure, great humor (mostly concentrated in the first half of the book), very well written, but an unrealistic and much weaker ending. Human is a real bipedal life form of midrange intelligence, living a largely deluded existence on a small, waterlogged planet in a very lonely corner of the universe.