Unlike some other reviewers, I wouldn't call Tides of War boring, but I will say it tries to do too much with too many characters in too little time. More specifically, it isn't that there are too many characters based on sheer numbers: it's that there are too many different stories being told at once, too many independent arcs. First we meet Harriet and James Raven, a newlywed couple separated when he's set off fight Napoleon's troops in Spain. We meet the Duke of Wellington, and Lady Wellington, who's finding her own independence while her husband is away commanding troops. Okay, fair enough. Seems like a manageable number of main characters, if a bit high for a 368-page book. But, no, here's an army doctor, a volunteer, a middle-aged army wife, a financier, an aide-de-camp, a weaver-turned-soldier, a painter, a widow.... oh, and who's that Herriers guy again? I count at least a dozen "main" characters in this book, in that they all get sections from their own points-of-view following their own independent storylines--no wonder this book is a mess. The storylines often don't intersect that much, there isn't much time to develop them, and in some cases I simply don't see the point. And it doesn't help that the characters are introduced in quite unmemorable ways, so it takes awhile to sort them out. (Speaking of unmemorable introductions, this book makes my all-time top two for "least interesting first sentence." But it does get better.)
Just as the book has too many main characters for its length, it also tries to deal with too many big issues--everything from the psychological trauma caused by war and the soldiers' difficulties in reintegrating into civilian society, to the technological changes inspiring the Luddite movement, to women's rights, to imperialism. The book is so overwhelmed with themes that it can't do any of them justice.
Also, there are some technical problems: there's a lot of "head-hopping," where the point-of-view shifts from one character to another without any page breaks to tip the reader off, and unattributed dialogue, necessitating re-reading to figure out who said what.
Tides of War isn't, however, an irredeemably awful book. The scenes themselves are interesting, the characters' personalities are well delineated for the amount of screen time they get, and the writing style is not bad. On many (most?) of the themes, I think Tillyard has interesting and insightful things to say; the book felt fresh in a lot of places, but before it could delve much into anything it was on to something else. The psychology of the characters felt real and the history was interesting. Unfortunately, this isn't enough to bring the book up to a higher star rating; it certainly has potential, and if Tillyard had had a better editor (and a more generous word limit?) it might have been a very good book. As is, though, I can't recommend it.
And a warning: the book has a fair number of potentially disturbing elements. There's a character who performs experiments in transfusion on animals, there's at least one detailed field-operation scene, and most notably, there's a brutal gang rape described from the point-of-view of one of the rapists. (By contrast, there's a minimal amount of battlefield violence depicted.)
Finally.... while I wasn't bored by the book, it was not compelling reading and I nearly didn't finish it. Two stars.