Dave Duncan has written two series with many of the same characters. The first series is A Man of His Word and the second is A Handful of Men. Because the two series are contiguous and share the same characters I am just going to review them together.
The first book, Magic Casement, from the first series was one that I liked and would have rated a 4 probably. I thought of it as a well-written YA fiction. The main characters in the book are teenagers and Duncan does, in my opinion, a very good job of expressing through the characters the feelings and viewpoint of teenagers even today. So I continued to read the series and Duncan did a poorer job of expressing the characters as they got older. But the progression of their growth and their stories was pretty well done and overall I would have given the series a 3.5.
While the first series was adventurous it was also more character-driven. The second series, which takes place 15 years after the first, is less character-driven and more political. Meaning political in terms of the disputes between the different regions and races. It could have been an excellent series based on that but it really wasn't.
The series is made up of all the mythical creatures devised by our world. Well, probably not all of them but a great deal. There are goblins and Jinn and pixies and fauns and trolls and so many more, including some I had never heard of. In addition, there are different locales inhabited by the different races. For example, the Jinnq live in awhat would be the Middle East today. (If you like world building, you probably wouldn't like that. It helped me to place some of the races and locales.) For me, given all the races, and their various characteristics, and their various locales, I found it exceedingly confusing. I don't know if that's because I needed a scorecard or if it was because the author made them sort of a muddle or whether I'm just not too bright, but I had trouble keeping track of all the players. And I should say, that there were a lot more players in this series than there were in the first series. And, in the first, the characters stayed together most of the time. They might have passed through a number of different locales but they did it together. In this series the characters were in pretty much all the locales but they went separately. So the stories would jump around between characters and locales. And sometimes a couple characters would come together and then they would separate, later coming together with different characters.
Finally, the climax and finale are a total mishmash. Seems that Duncan wanted to tie everything together in a pretty little bow in a very big hurry. As a result, the bow was squished and untied in places and just ugly. So if I were rating just the second series, I would give it a 2.5 and that might be generous.
In summary, I had to give the two series an overall 3. I really couldn't give it less since I read all 8 books. But if I had to do it over again, I would read the first series but not the second.