There's a huge historiography on the Spanish Civil War, both in English and Spanish. Beevor is a good starting point; the other survey history I'd suggest reading is Hugh Thomas' The Spanish Civil War. It's dense at times, but mostly very readable and it's a more sophisticated history of the war than Beevor's. Others will recommend Paul Preston's histories (there are several), but I'm not a fan.

Other texts I'd recommend:

• Stanley Payne — The Spanish Revolution: this is excellent on the social and economic revolution and counterrevolution in the republican zone, and the evolution of the late Second Republic.

• Ronald Fraser — Blood of Spain: this is a peerless oral history of the civil war; some really fascinating perspectives on how and why the war unfolded as it did.

• Raymond Carr — The Spanish Tragedy: another of the great Hispanists. Well worth a read.

There's lots of super-specialised texts on specific aspects of the war and Spanish society (including a lot of economic history, if that's your thing?) but the ones I mentioned will give you a really good overview.

I'll echo /u/k1990's recommendations of Beevor and Thomas as well as Payne. Unlike /u/k1990 I am an advocate for Preston's works, despite his bias. The Spanish Civil War is quite good, and The Spanish Holocaust is outstanding. Jose Sanchez's The Spanish Civil War as a Religious Tragedy is not only the best english language study of anticlerical violence during the Spanish Civil War, it also is excellent for the peculiarities of the Catholic Church in Spain before and during the conflict. The author is Catholic, but rather than apologizing for Franco he calls the regime "barbarous" and deconstructs the concept of a crusade in Spain. Another little-read gem is Jose Antonio Aguirre's book Escape Via Berlin, which covers his time in office as President of the Basque territories as well as his improbable but true escape from the Nationalists and the Nazis in the aftermath of the Spanish Civil War.

You didn't ask this question but i'll answer it anyway: the books you want to avoid are any that do contain the concept of a "crusade" by the Nationalists as a good thing. They are uniformly awful.

Only after reading three or four books on the SCW would I recommend going to Orwell or Hemingway. It's not that their books aren't good (they're great, actually), it's just that their unabashed (and understandable) bias can unduly color your reading of other works. After you know the basics of the war Orwell and Hemingway's commentaries really become excellent.