I don't understand why so many Wicked fans despise Son of a Witch.
If I remember correctly, I felt that there were some big issues with continuity between the first and second books... but maybe it's just because there was such a big gap between my reading of each book. I didn't hate the book, but I didn't really care about any of the characters, or what happened to them. Granted, this was years ago and I might feel differently after a second read.
Son of a Witch is pretty different from Wicked, too. I don't remember it continuing much of the politics that Maguire set up in Wicked. Honestly, you don't really get any loose ends tied up until Out of Oz. Of course, Maguire makes sure to create more loose ends as he's tying up ones from previous books, the clever bastard. I definitely felt more for the characters in this book than in the previous two books.
A Lion Among Men was decent, but I listened to the audiobook with half an ear and I think I missed a lot of the key parts.