When Pastoria is introduced into the Oz books in Land, most of the details of the character from the play are dropped, but he's still referred to as ruler of Oz (or at least of the Emerald City area) prior to the Wizard's arrival. Glinda sees his daughter Ozma placed on the throne, and the former king is pretty much forgotten for a while. Ozma's only mention of her own father in Dorothy and the Wizard is to say that he was imprisoned by Mombi. It was left to Ruth Plumly Thompson to give us the details of Pastoria's fate, which she did in Lost King. According to Pajuka, Pastoria's Prime Minister whom Mombi had turned into a goose, the King was kindly and absent-minded, and had trouble suspecting ill of anyone, which was a large part of why the Wicked Witches were able to gain so much power during his reign. Mombi enchanted him and then forgot what she did with him (possibly a side effect of the magic-sapping potion that Glinda forced her to drink), but later becomes interested in finding him again, suspecting that restoring him to the throne would be beneficial to her. I don't want to give the plot of Lost King away, but I don't think it would be spoiling too much to say that Pastoria is eventually found and restored, but he doesn't retake the throne. One other thing about the book that I found interesting is that Ozma claims to remember hiding out from Mombi in Morrow, even though she was a baby when Mombi enchanted her. That's a fairy memory for you, I suppose. Anyway, Pastoria is mentioned in a few subsequent books, but never has a major role in the rest of the Famous Forty.
There are, however, some apocryphal Oz books that seek to answer a question that the canonical authors never addressed, which is whether Pastoria was married. Magical Mimics presents him as old and childless when Lurline leaves Ozma with him, but doesn't specify whether he has a wife. While I haven't read it, I understand that Ray Powell's Mister Flint in Oz says that Pastoria's wife's name was Ozette, and that she was enchanted by the Wizard using Mombi's magic. Since Lost King establishes that Pastoria was already out of the picture by the time the Wizard showed up, I find this unlikely. Another account of the lost queen's fate appears in Dennis Anfuso's The Astonishing Tale of the Gump of Oz, in which she was enchanted by Mombi, and her name is Cordia.