Subject No Object
A quick look at Amazon reveals that there are lots of books on Astrobiology. Cambridge has a series on the subject. We even read that NASA is pivoting to astrobiology. The only thing missing to make the subject more vital is an object of study. To date, we have zero evidence of extraterrestrial life of any sort.
Given the tantalizing prospect, though, textbooks are being written, and they are firmly grounded in the life the only place we know of it. That's a good idea, I suppose, and based on the notion that any life that we do discover will look a lot like that on Earth. Is that reasonable?
The more we learn about life, the less plausible substantially different living systems look. The unique virtues of the carbon based system seem hard to emulate in any other chemistry. Of course, we may just lack imagination.
If we do discover signs of living extraterrestrials, it would certainly be one of the most consequential discoveries of all time, but it seems a bit early to me to get our hopes up. I hope I'm wrong.