Beware! Here Be Spoilers!
I enjoyed The Librarians so much that I've ordered Season Two and the three films that came before the series. This is just the sort of light hearted, witty, fun TV that I like!
Two or three episodes into the series, I remembered why the name Christian Kane sounded so familiar. He's the actor who plays Jacob Stone, the oil rigger/art history expert - and he used to be Lindsey MacDonald, the evil lawyer who worked for Wolfram and Hart in Angel! This time, he's firmly on the side of the angels (though I did wonder if he was going to suffer from "evil hand issues").
It took me a while to work out what sort of accent John Kim (playing Ezekiel Jones) was using - but eventually someone mentioned that he's supposed to be Australian....
So, our intrepid heroes and heroines are sent on several missions, usually by the Clippings Book, which collects information about magical happenings around the world, but once by a phone call from Mother Christmas (or "Gretchen" as Jenkins called her) for a delightful Christmas episode in which Santa is seen in several different manifestations, including Odin, and we learn that Colonel Baird's first name (which she hates) is Eve, because she was born on Christmas Eve.
There are also dragons, a haunted house, a labyrinth with a Minotaur (in Boston), and all the cast have the opportunity to do different things - as Ezekiel learns what it's like to be Santa, for instance (he doesn't like it), or Cassandra becomes Prince Charming in a town (named Bremen) where fairy tales are coming true.
We also learn, through the series, that Jenkins is something more than he initially appears (a knowledgeable recluse who just wants to be left alone to do his research) - especially when Morgan le Fay recognises him. That was in the episode about the high school science fair, which had a guest star (Bex Taylor-Klaus) who I recognised as the street kid in Arrow who idolises Black Canary. This time she was playing a brilliant science nerd (with an appalling mother and a Goth boyfriend).
Flynn Carson turns up occasionally through the series, as the original Librarian who is searching for a way to retrieve the Library from the Void - and the very last episode ties together all the previous episodes in one long arc, very neatly indeed. It seemed that each quest was random and self-contained, but they brought together everything they needed to magically restore the Library by the end. Of course, Dulaque and the Serpent Brotherhood are also in the background, also wanting to get their hands on the Library.
It's fairly obvious who Dulaque used to be - there's an Arthurian strand running through the series, and Morgan le Fay turns up half way through - and the reveal of Jenkins as the only Knight of the Round Table who could best Lancelot was glorious!