This book reads like two stories glued together. The first half tells the tale of how Sharpe comes to be in the service of the brother of the Duke of Wellington, who is the British ambassador in Cadiz. Wellesley Junior needs to obtain some ill-judged love-letters that he has written to a very unsuitable woman. Sharpe and his men, who have arrived in Cadiz after a bruising mission to blow up a bridge, are enlisted to aid Wellesley buy back his letters. This story, of intrigue and murder amidst the old town of Cadiz, is very well told and excitingly paced. The opening bridge-blowing adventure is also highly entertaining. As with so many other Sharpe novels, the reader is left wondering whether British officers of the day really were that stupid and pig-headed.
However, the second story of the Battle of Barossa seems like it belongs in a different novel. Even Sharpe and his men realise that as they say on several occasions "we shouldn't be here". The plotting that gets Sharpe & co onto the battlefield is very contrived (Sharpe is brave and an outstanding soldier but usually does not willingly put himself in such danger if there is no good reason to do so) and most of the action concerns a new set of characters who have only had walk-on parts (at most) in the first half of the novel.
This is not to say that the account of the Battle of Barossa is anything other than exceptionally well told, but it just belongs somewhere else. Cornwell does at least bring to life the British senior officers whose fortunes we follow (until Sharpe turns up) and his description of battle is, as always, outstanding. Perhaps the author is seeking to contrast the earlier incompetences of Sharpe's initial mission with the stout-hearted professionalism shown in this battle. There is a "baddie" from that earlier mission who Sharpe wants to polish off, but why wander around in a bloody, corps-level battle to look for a needle in a hay-stack?
So while the book is an exciting read and is full of Cornwell's usual flair for the feel of this period, the need to have Sharpe appear in every major battle of the Peninsular War is becoming a little tiresome and, in this case, unconvincing.