I rarely read books twice, but Catspaw I've read three times since finding it, and with each reading I look forward to the next one even more (although what I always WANT to look forward to is another book that I become as personally involved in as I did this one).
Joan D. Vinge doesn't just make Cat a character you can really identify with and care about (as other reviewers have noted), but he lives in a world that the reader becomes involved in because it is at once alien (and thus intriguing) and ultimately recognizeable: this Cat shows with his affinity for the low-class garment denim jeans, which have lost favor in an era of highly developed fibers and deep space travel. I was amused by Ms. Vinge's workplaces, staffed with secretaries and clerks as they always have been, filing and answering calls while also using equipment that we can scarcely imagine. After finishing Catspaw the first time, I ached to find a threedy, don its net, and surf it just as Cat would have done...
Too often the world that a sci-fi writer creates is so drastically changed or alien that it is impossible to relate to, but Catspaw makes you feel like you'd really caught a glimpse into the future and seen how life would really be. Cat describes the places and organizations he encounters just enough that sooner or later you can make a mental archeological jump between its name and his description to figure out which presentday familiar place or organization lies deep at the heart of its past. Many place name (N'Yuk), organization names, and object names ("threedy" for three-dimensional "television") have evolved, but in such a way that the reader doesn't need a glossary, their evolution makes etymological sense, and their use is as natural as the English we speak today.
Most importantly, Ms. Vinge displays a rare understanding of both individual and group psychology/behavior, and of their interplay and composition. Too often I am frustrated by authors whose work is limited to interesting individuals in unrealistic societies or the larger movements and problems of societies whose individuals are hard to relate to, but Ms. Vinge's characters and societies have real depth. She has the ability to portray individuals, family groups, corporate groups, political groups, the media and the objects of their attention, friends and the friendless, strangers, gangs, loners, and all everyday people with the mixture of immediacy, objectivity, compassion and understanding that really gets a reader involved, and in none of the books of hers that I've read so far (five so far) does she do that as well as in Catspaw. On top of that, her prose flows so easily and naturally that the reader is involved before she or he turns the first page. I'll be reading Catspaw again within the year, I'm sure, and possibly Psion and Dreamfall as well; I only wish there were more books about Cat's adventures for me to explore.