And really glad that you got so much good from reading MacDonald. Shall I recommend more?
If you're looking for a single book that stand alone, try "The Minister's Restoration". For characters that are developed in a series, try "The Tutor's First Love", "The Musician's Quest", and "The Maiden's Bequest" (Also available in a single volume, like the one you just finished. These revolve around Hugh Southerland and Robert Falconer - two of MacDonald's most famous characters).
It may interest you to know that George MacDonald was close friends with Mark Twain; they visited each other's homes and read each other's stories to their children. The Twain children's favorite book by MacDonald was "The Back of the Northwind" -- the only thing I've ever read by him that I thoroughly DISliked!
C.S. Lewis considered MacDonald his mentor, and mentioned him in every book he ever wrote. Lewis' favorite was a fantasy book called "Phantastes" -- which I've never read.