Late september/early oct seemed like a good time to go, not terribly busy or hot, although the main cities were still busy for sure: Séville very busy while Cordoba not at all for instance. Getting tickets for the Sagrada Familia in Barcelona was essential still while some other attractions would have had manageable enough waits, even if it was fine to skip them anyway where possible with advance tickets. Weather was still quite varied between sweating in Barcelona and quite cool in Madrid (down to 13C one day).
And yet, despite the temps that were more than ok, some cities still had stupid and pointless siesta hours that closed most everything from 14:00 to 16:30, really fucking up sightseeing (Hello Zaragoza, get a clue if you want more tourists, especially as a day trip from madrid with quite expensive fast train tickets). On the plus side, this is mostly going away in many cities, or wasn't relevant in October which wasn't considered summer anymore.

History wise, it would take me a while to go through it all, and I wouldn't do a good job anyway, but long story short the muslims invaded part of Spain and stayed a few hundred years until Christian crusades took them all out and destroyed all their mosques except for a select few (and the one in cordoba got an unsightly church built in a very middle, seemingly as a "fuck you"). The Jews also picked the wrong religion apparently and were invited to convert (eh, they only had to accept Jesus, and a few extra books), or were cordially invited to leave. A few remained underground and kept their faith while pretending to be christian and eating pork in front of witnesses.

I can't stay I really support bull fighting, but it was interesting to learn about the history and culture around it, as well as seeing the bull rings, and even a bull raising farm.

Food was good overall. My sampling palate enjoyed the tapas that most restaurants offered, sangria as well, and the many different ways you can eat pig :) (including milk fed pigglets).

The trip, thanks to Rick Steves suggestions (and I'll say that Rick Steves book seem frozen in time and lack really needed updates, as well as in the case of Spain providing a very questionable suggested routing, so we had to work hard to make our own that made more sense, thanks Arturo for the help there), we did go to see UK's Gibraltar which is worth the trip (and unlike what the book said, will happily use your euros if you don't have british pounds), and the day trip from Tarifa to Tangier, while not strictly necessary, was educational, especially with our private guide.
Not unlike France, most of the south is hard to visit with a car, but once you get to Madrid, public transport works fine. Going through smaller towns like Ronda was worth the car, though.

So, that was that for Spain, nice trip, most everything went according to plan. Here is the route: