I'm a sucker for any opportunity to do research, so I looked up the Battle of Barossa that supposedly figures in this one, and it took place in March 1811. So that puts it after Sharpe's Escape (1810) and before Sharpe's Battle (May 1811). Guess that makes it about in the middle of the series, as you feared.

That sounds like a good thing to do, though -- reread them all in order again. Let me know when you start, and I'll do the same!