Which Narnia book by C.S. Lewis was published second?

Prince Caspian was the second Narnia book published by C.S. Lewis.

Geoffrey Bles published Prince Caspian in 1951, one year after The Lion, the Witch and the Wardrobe. Its full title is Prince Caspian: The Return to Narnia. The story brings Peter, Susan, Edmund, and Lucy back to Narnia, where they help the rightful heir, Prince Caspian, resist the Telmarine ruler Miraz.

The book is second in publication order but fourth in the commonly used internal chronological order of the Narnia stories. That distinction is a frequent source of confusion. Lewis did not write the books in the same sequence as the fictional history of Narnia.

The novel expands Narnia by showing how its earlier golden age has become a distant memory. The children’s return is therefore not simply a repeat of their first visit: they must help recover an older tradition and restore Caspian’s claim to the throne.