By the standards of key works on Spain's Civil War this is fairly concise at about 300 pages. However its value to students of the period is far more than this (possibly partly because it is so tightly structured).
This is not a blow by blow account of the war. For that the newest Beevor work is probably better. Rather Preston takes a loosely narrative structure and uses it to examine the key themes produced by the conflict in a clear and perceptive manner. The initial chapters setting the context should be compulsory reading not just for those interested in the 1930's but for those who want to understand modern Spain. The divisions and splits apparent before 1930 still figure prominently today: the historic poverty of the rural south and west still shows in the fact today that these areas are hardest hit by "la crisa". The separatist tendencies of the Basques and Catalans similarily predate the Franco and Post Franco era.
The complexities of the political infighting of both right and especially left in the 1930's is an area that can confuse and make the period difficult to fathom. Preston does an excellent job of navigating the reader through the ebb and flo of the politics helped by a list of key figures and a glossary of key terms attached as appendii. I found his treatment of the international aspect of the war most illuminating. Not just the intervention of Italy and Germany but also in making the less obvious war aims of the USSR evident. Most of all he shows up the at best perfidious, at worst antagonistic attitude of France and especially Britain to the legitimate Republican government. Officially peddling non-intervention, this did little more than cloak indirect support for Franco and the nationalists. It was left to the International Brigades to restore some dignity for the western Great Powers.
The full title of the work includes, "Reaction, revolution and revenge". It is the final section that may provoke most thinking by those new to the period. Revenge was displayed by both sides. The Republic, especially early on was guilty of unprovoked attacks on clergy, property owners and "fifth columnists" killing many thousands. Yet Preston shows how attacks, reprisals, disappearances became part of the systematic advance of Franco's forces and supporters. Indeed Preston argues the war took so long to end as a consequence of Franco's desire to eliminate possible future Left and Republican opposition as his armies progressed through Spain (rather like the actions of the Red Army outside Warsaw at the end of the Second World War as they waited for the Germans to eliminate the non-communist Poles of the failed Polish uprising before the Red Army itself entered the city to liberate it from the Germans). This revenge led to not just secret killings but also mass imprisonments in labour camps and the continued impoverishment of what were the last Republican areas of control for many years after the end of war.
In his introduction, Preston makes clear his sympathies are with the Republic rather than with Franco. However he does not let this show in his writing – and is to be commended all the more for telling readers this.
For actual students of the period there is one further gem. The final chapter is a comprehensive and very well explained critique on the works available on the civil war. This in itself makes reading worthwhile!
linked casahistoria site: Spanish Civil War