There's a couple of things that really set James Goss' Risk Assessment apart from other Torchwood novels.
First, there's the introduction of a great new character, Agnes Havisham. Havisham is the Torchwood Assessor, the person responsible for overseeing all Torchwood operations around the world and with the power to close them down if they get out of line. However, Havisham is kept in a perpetual state of suspended animation and awakened only when computers sense a moment of great crisis--something that has only happened four times in the last century. The best thing about Havisham (a Victorian-era spitfire of a woman) is that she's the one person Captain Jack is afraid of--indeed, instead of his normal cool and suave self, he comes across as a bumbling pretty-boy when in her presence. It's rare to see Jack out of his element, and the novel has quite a lot of fun with the situation.
Second, the book has a really nice twist about half way through. Normally, when the heroes attempt all kinds of crazy schemes to stop the big alien menace (in this case, a galaxy-devouring entity called The Vam--which seems rather similar to The Gordian from the story in Torchwood Magazine # 14) we know they're going to fail until finally hitting on a solution in the last chapter or two of the book. Here, however, they dispose of The Vam surprisingly quickly and then we learn that the real threat is something that has been properly hinted at but easy to overlook. Good stuff.
There's also some nice continuity with other Torchwood tie-in products: a new speedboat named The Sea Queen II since the first one was destroyed in The Sin Eaters audio book; a mention of Torchwood India, last seen in The Golden Age radio play; and a chapter set in the Skypoint Apartments from the novel Skypoint. There's also some fun flashbacks to previously unknown adventures that Havisham and Jack have shared, as well as Jack having experimented (and failed miserably) at being something other than a Torchwood operative.
I thought the end was perhaps a bit too jokey, but Goss definitely created a great character in Agnes Haversham--one I would love to see again.