In this YA novel, Jim is fourteen and a werewolf, although he's not a fully developed werewolf yet like older brother, Dave. Becky, Jim's sister (adopted, not blood), is a witch, and Barry, an exchange student living with them, is a martial arts expert. A golem patrols their house and the nearby lab when needed, and it's needed the night Jim's dad disappears. There's blood on the floor, and the transcomp machine is damaged.
About that transcomp machine. There are all these parallel worlds, see, and the machine is used to travel between them (lightworlds, grayworlds, darkworlds, deadworlds). So where's old dad gone, who attacked him, and what the hell is going on?
A lot is going on, and frankly I'm not sure I kept up with all of it. There's a war going on with one of the darkworlds, and Jim's dad is involved. So is his brother. So dad is probably in one of the other worlds, but which one and how to get to it? Did I mention that Becky is a witch? Maybe she can arrange for travel between the worlds with magic. Yep. Sure enough.
This is a very short book, a novella, really, and there's a lot going on. So much that everything is given short shrift. I like short books, but this is one that needed fleshing out. Zelazny does bring all the different plot lines together in the end, which introduces a clever twist, but it's not up to his best work.