I read this book as a standalone novel, and am reviewing it as such.
My first impression of this book was that it was low-quality pulp sci-fi. A few chapters in I realized I was being far too harsh. Jack Chalker is a talented writer and there's much to like here. There's a lot of vivid detail and the prose is laced with subtly whimsical humor throughout, making this hard sci-fi work an enjoyable read. There are a number of unique and memorable characters. I particularly liked Marquoz, the small dragon-like detective who lights his own cigars, and Obie, a moody supercomputer who controls a planetoid that doubles as a spaceship.
My problems with the book were all plot-related. First, there's very little action. Mostly it's exposition or expository dialogue. Second, the plotline does an annoying switcheroo about a hundred pages in. Early on it appears the book will be about a serious threat to all of the known races in the galaxy. Then, suddenly and rather undramatically, the threat is neutralized but a new one arises in its place. Most of the characters and storylines are dropped and a new set of characters are introduced for the second plotline (which has nothing to do with the original one). A third problem is that while the action finally picks up toward the end of the book, nothing ever gets resolved. The ending is a cliffhanger, "will our heroes succeed in their quest" kind of thing. The upshot is, I kept reading this book because it was witty but I couldn't care less what happened next. I'm glad I read this book, but I don't think I'll bother with book 5, despite the direct feed-in.