Lev Grossman at The NY Times:
Since the last volume of “His Dark Materials” appeared in 2000, Pullman has written two more (superb) volumes of a second trilogy called “The Book of Dust”, as well as a few interstitial bits and bobs that fill in the odd blank spot in his vast legendarium. His latest work, “Serpentine,” is one of the latter, and as befits its title it is the slenderest of creatures, almost plotless and at 80 generously illustrated pages barely thick enough to have a spine. Set five years after the events of the first trilogy, the story finds Pullman’s heroine, the unquenchably curious Lyra, in an unquiet state of mind. She was once (in “The Amber Spyglass”) briefly separated from her daemon, Pantalaimon, and ever since then she’s been haunted by the question of what he did while they were apart.