I was actually introduced to this series in 1974, but didn't track the rest down for a couple of years. I love these books and have read them over and over, so.... These are wonderful reads and have a personality all their own.
This is a fantasy not to be missed. The first series is superior, but they are both good reads.
Should I give any details? Can I without spoilers? These are great.
The world building (multi-verse building?) here is not only superb but it's so well incorporated into the overall tale you really don't think about it all that much. That's saying something as it's one of the more "sweeping" creations in fantasy. The characters in this series are complete, true to themselves, and detailed without a lot of wordy description getting in the way of the story. I'd say that the books (the story) is plot driven, but I don't want to mislead. It in many ways is both character and plot driven. Very well done, at least in the first series. While the second series is the weaker of the two it to is enjoyable and worth reading.
Okay..no spoilers. These are highly recommended and if you're a fantasy fan who hasn't discovered them I think you have something to look forward to.