Voyage to the City of the Dead by Alan Dean Foster is the 5th book in his Humanx Commonwealth series. This series is quite long (something like 28 novels!) and I haven't finished it yet, but it's also great science fiction, especially the first half-dozen books.
The later books are good, but not quite as good as those first six. If you'd like to give them a try, you should try to read them in order since they do follow a continuing story line.
You can find the chronological order of the books on his website under the topic 'Chrono Data'.