Greetings! In addition to checking out the resources that moderator u/crrpit has linked in their response, I'll see if I can try and lend a hand with the (admittedly difficult) skill of reading history in preparation for an essay. Here are a few tips that have worked for me in the past.

• Look for key points: A lot of reading material will have several arguments within it that attempt to argue a certain stance (e.g in this instance one source might argue that World War 1 was a global war whilst another might not). Usually the material will be organised based on these arguments, and each chapter/sub-heading will concern a different point or a related argument. It helps to skim and scan the table of contents beforehand in order to see if there are particular areas of the book which might help you out more than others. For example, I imagine a chapter titled "the war in the Middle East" or something along those lines would be of more use to your essay than "origins of the war." Go to those chapters first, and focus on extracting the key information from each chapter which helps support your essay. That brings me onto my tip...
• Points first, then evidence: Chances are if you're already reading for an essay, you have a rough idea of whether or not the First World War was a global war. That does not mean that you have a clear idea of what each point might focus on or use as evidence. Instead, what it means is that you've roughly outlined what areas of the prompt to look at (e.g one paragraph/section might be dedicated on how the war was physically fought in more battlefields than any previous war, whilst another section deals with how the global economic system was impacted by the fighting). Based on these "general areas", that helps to narrow down what you're reading and taking notes on. Looking for facts about how the Middle East, Asia, and Africa were involved in the war? Skip the reading sections about Europe and America and go fact-hunting for those bits of information. You might want to go back to the European countries and America later down the line for another point, but structure your reading around the general flow of your essay.
• Quotes are good, but not gold: It might be the case that your notes are filled with quotes from the historians/authors of the reading material. While these historiographical statements are certainly useful to enhance the strength of your essay's arguments, they are not essential to ensuring that your essay covers the prompt well. It's grand if you can integrate a subjective quote from a historian or two into your argument, but they won't help you support your point about the objective areas where the fighting of the First World War happened. Look back through previous notes; if you find you're taking too much time to copy word for word what the historians are saying, try and paraphrase their arguments instead. The bottom line is that your notes should fit with the essay, and thus getting the facts should be your first priority.

Of course, in an area with complex and oftentimes daunting literature such as the First World War, there can be more problems with reading and taking notes quickly. As someone who has had to read a fair few confusing historiographical articles and books on the matter, feel free to pm me if you'd like further help or just want some more sources to point you in the right direction. Hope these tips help you on your essay-writing journey, and do feel free to ask some follow-ups as you see fit.

Hi - we as mods have approved this thread, because while this is a homework question, it is asking for clarification or resources, rather than the answer itself, which is fine according to our rules. This policy is further explained in this Rules Roundtable thread and this META Thread.

As a result, we'd also like to remind potential answerers to follow our rules on homework - please make sure that your answers focus appropriately on clarifications and detailing the resources that OP could be using.

Additionally, while users may be able to help you out with specifics relating to your question, we also have plenty of information on /r/AskHistorians on how to find and understand good sources in general. For instance, please check out our six-part series, "Finding and Understanding Sources", which has a wealth of information that may be useful for finding and understanding information for your essay.