There's little in this book that will surprise an experienced adult reader of fantasy. For younger readers, though, Taran Wanderer is a pretty fine book It's a solid discovery adventure that never loses track of the fun, while still being packed full of solid, serious morals about values. Even without Eilonwy, this is a much stronger and less formulaic offering than the previous entry, The Castle of Llyr. It's the quintessential 'finding what you weren't looking for' story.
Despite the strong story and the easily swallowed morals, it's not perfect. In particular, Alexander continues to completely bypass Gurgi, the most interesting character in the series. He continues to play loyal, devoted servant, and to be broadly unacknowledged. For example, Taran spends a good portion of the book making things - always for himself. Not once does he think, 'Hey, Gurgi stands by me and keeps saving my life. Maybe I should do something for him.' It's a disappointment, and a missed opportunity that actually undercuts the book's moral messages.
Regardless of that flaw, Taran Wanderer is a fine continuation of the series, and well worth picking up.