Thank Spain's lucky stars that Napoleon did not put Jerome in charge. The country would be bankrupted in less than a year. Louis would have been ideal but I read somewhere that he would have refused. I think that Napoleon, (being mortal ,) off the battlefield anyhow, is allowed some errors of diplomatic judgement as even the great Hannibal Barca was pretty useless in the diplomatic arm, which towards the end of his campaigning days, was fatal.
I am always surprised to read about the Spanish army at the time being second rate, and Napoleon was a bit lucky in having to face a Spain which had it's treasury and army and to an extent fleet, allowed to slip into a coma as Spanish might at the beginning of the eighteenth century was still impressive. If Wellington had not taken the pains of re-organising the British army - Soult and Massena would have been more impressive. I am always surprised at Napoleon indulging Soult - I think he should only have been a General. Victor understood Wellington much better.
Financially , it was a bad move to invade Spain, but you would definitely not want a resurgent Spanish fleet funded by British money harassing your sea trade routes. I think that Napoleon was thinking a lot forward to the day that he could pile money into building a huge french fleet allied to a Spanish one and redress the loss at Trafalgar. Nelson was dead and who knows who would be the victor a second time round. English paranoia over a credible threat to their fleet, I think played its part in concentrating Napoleon's finances and attention on land rather than at sea.
It all adds to the overall flavour of Napoleonic campaigning as french forces fought in sand , mud, snow, steppes, mountains, plains, forests, swamps etc. Got to see the capitals of Europe for free and sample the food etc- the original tourist nation. Fly Napoleon Eagle Airways - the only way to fly........
As for books, I do not know what the situation is in the States or Spain, but the " recession" has decimatrd the number of second-hand bookshops and whereas a decade ago, you could find amazing and cheap stuff on the Napoleonic period- you cannot now- yes there is E-bay but even tat sells for quite a bit. There is only one remainder bookshop I know of now whereas before there were lots, and they used to be great at selling American Civil War books at crazy prices, as well as the generalised Peninsular war books.
I bought a hardback on Chancellorsville for £4 in a charity shop over Xmas - but no Napoleonics.
Napoleon's " natural border " is what he deemed it to be in his mind, which unfortunately does not conform to national but international boundaries. :laugh: