I also love this book in many ways. All design needs to be speculative to a degree, even the most practical, otherwise you're designing for the past. Any design project takes time, so you at least have to speculate on the context for the near future when the product/service/etc will be released. The best products speculate far enough into the future that they create entirely new "needs" - they fill a gap (practice and/or desirable) that isn't here yet, and they also inspire people to think about or experience the world in a new way.
@Kristian I love hearing that things like this are helping students find their individual voices. Great design not only addresses something practical, but also brings a new and subjective perspective to bear on that problem space.
There is some very valid criticism of the current state of speculative practice around it's narrow world view and problematic definitions of what the "present state" looks like. Here's a good place to start on this: https://medium.com/@luizaprado/questioning-the-critical-in-speculative-critical-design-5a355cac2ca4