If you read my review of The Cuckoo's Calling, you'll know that I enjoyed it, but wasn't wowed by it. The Silkworm, though, was much livelier- a more complicated plot, more fully-drawn characters, and action, action, action.
In this, Detective Cormoran Strike's second high-profile case, a controversial writer goes missing, and when his wife turns to Strike for help, the result is a story of revenge, brutality, obsession, sex, and murder. The London publishing world, with its writers, agents, editors, and publishers (and their relationships), becomes a kind of underworld, where adulterous liaisons and shifting allegiances influence who publishes whom and who can bring out the next bestseller. And when infamous writer Owen Quine threatens to self-publish an "obscene" novel taking down almost every one he knows, and then winds up murdered in a grotesque, sadistic manner, Strike is hooked.
Both Strike and his assistant, Robin, are developed more fully in The Silkworm, where Robin finally articulates her interest in apprenticing with Strike, rather than just answering his phone and making appointments. We also meet more of Strike's family and friends, and we can begin to anticipate his strategy, if only in the most general way. (After all, I'm terrible at guessing who the murderer is before the author tells me).
Like Stephen King's most recent novel (also crime fiction), Mr. Mercedes (2014), The Silkworm is very meta-literary, since Strike uses his analysis of Quine's writing in his investigation of the writer's murder. The writings of Quine's friends are also crucial, and the literary world itself is turned inside-out as Strike unravels the complex web of relationships and lies that undergird it.
So like I said, I think this second Strike novel was even better than the first, and I'm looking forward to the third.