On the whole, I can't think of too many things wrong with Gary Russell's "Instruments of Darkness". Especially if your expectations have been dulled by, say, "Divided Loyalties" or "Invasion of the Cat-People", you might be happy to find that not all that much in this book is risible.
On the other hand, I can't think of too many things I liked about it, either. I don't know what I would say, for example, if I were asked to recommend it to others. I'm not a 6th Doctor fan by any means -- not on TV, not in print -- so this less over-the-top print version of the Colin Baker Doctor does not get me excited. I liked Mel as a companion, but this book's contribution to the post-TV companion canon -- Dr. Evelyn Smythe from the Big Finish audios -- was a letdown.
Evelyn takes up large portions of the text, without really adding much. She's introduced as a character not through her actions, but by long-winded speeches -- by speeches by the Doctor; by her duelling monologues with Mel (I hesitate to call them "conversations"); and, worst of all, through her own speeches. We keep hearing about how great she is. Fine. Go out and prove it. Do something heroic. Be less annoying.
When "Instruments of Darkness" isn't about Evelyn, or about Evelyn's relationship with the Doctor (she's introduced as a jilted former companion), or about what Mel thinks of Evelyn... there's a convoluted plot about alien beings (think Trelayne, if the Squire of Gothos had a less self-aware younger brother) perverting the course of human history. There are telepaths in France and Auton telepaths in England. There are a couple of well-drawn American reporters, but they're limited to about 12 pages of text (set in Micronesia, would you believe) and could be eliminated from the story without a hiccup. The end of the book is meant to be tragic, but it ends with the self-sacrifice of a zero-dimensional quaternary character, so... if you can figure it out, you can enjoy it. At least you'll be able to say, "I never saw that one coming!", and mean it.
"Instruments of Darkness" takes 70 Doctor-free pages to get going. The first original "Doctor Who" novels published in the early 1990s did well with this approach. Here, however, the space is used to introduce about 20 characters in short, violent, action/tragedy sequences. Coming at the end of the novel, such a montage could have provided kick. Coming at the beginning, however, it's a drag. Who are these people? Why do they then vanish for the next 150 pages?
So, let's recap. I've complained about the plot, I've complained about the characters. Now, let me switch gears and kvell about the villain. Remember that annoying habit the New Adventures had, of bringing back old TV companions, ruining their lives, turning them against the Doctor, and killing them off? Well, one of the human villains of this piece is a familiar figure. Not from the TV show, but, for once, it's a pleasure to bring back someone else just to ruin their lives. That's why I give the book extra points and that's why I owe Gary Russell a beer.