This is more of a commentary on both books in the series to date, but I'll focus on Peril for the sake of relevance. Up until recently, most of my alternate history experience has been limited to Turtledove, who, although he overlooks many small points about causality, paints a picture of an interesting and fairly believable world.
Then, I began reading the S&S series, expecting an informative development to an interesting idea (Britain attacking the U.S. during the Civil War). It was a total letdown. I have never read any of Mr. Harrison's works previous to this, but I do not feel any particular desire to now.
He portrays every character in one-dimensional descriptions, based along the lines of U.S. = good, everyone else = bad. He doesn't even take the time to develop any of the non-U.S.-and-allied characters beyond their immediate motives relating to the war and their own pompous convictions, regardless of what kind of person they were in reality. Though I know little about the actual Queen Victoria, I am more than a little suspicious that she did slightly more than scream at bad news and throw incessant fits.
Likewise, the lack of real development of civil issues in the reunified U.S., primarily the treatment of freed slaves, was irritating. That most people would practically ignore the existance of a problem save for philosophical argument is almost mind-boggling, and the section dealing with a negro teacher in Mississippi is resolved with impossible simplicity. Why no social backlash? It wasn't even mentioned again, and given the magnitude of what happened it could easily have sparked major riots at the very least.
Finally, issues abroad. I find it more than a little unlikely that the British would make such a pointless effort at building a road across a several hundred mile section of mountain and jungle in a country the U.S. has major interest in. Wouldn't it make more sense to build a road across Panama, near to where the canal is? The distance is much shorter, the terrain more hospitable, and it's much more remote from the U.S., making attack harder and it's existance more difficult to be known about. In fact, why didn't the British just bring their Asian troops around the world the OTHER WAY? By going around Africa from Asia would take only a little longer than crossing the whole Pacific, landing hundreds of thousands of troops, crossing harsh country, then reloading the troops (on ships that would have had to be in the Atlantic ANYWAY). The author makes huge logical errors on the part of the British.
And the Irish invasion! Why would the British just give up on Ireland after one week, attempting just one troop landing? And that the resulting situation would be so stable even after the Americans had left, as in Canada in the last book (since when do ALL the British live in just three cities, then give up after each is attacked?).
I will read the last, although I can imagine how it will finish. Mr. Harrison may even throw in some suspense for once.