For a far more extensive list of World War I reads, I would highly recommend checking out the AskHistorians booklist on the topic, as u/LateToThisParty has already linkdropped. With regards to the "Top 3" reads on the First World War however, this all comes down to what exactly about the First World War you would like to learn more about. Whilst the majority of works focus on the actual military history of the war, there have been plenty of great works on lesser-known topics such as the home front, cultural impacts of the conflict, and the peacemaking processes during the Paris Peace Conference. As u/TheHistoriansCraft's comment notes, there are even country-specific narratives which focus on one belligerent during the conflict.

The following books, as such, should serve as more "general" reads on the three key stages of the conflict: initiation, prolongation, and termination. Where possible, I have also included "alternative" works on the similar period.

Initiation

• Top pick: The War That Ended Peace: How Europe Abandoned Peace for the First World War (2014) by Margaret MacMillan - This is a great pop-history work on the "long march", as one reviewer terms it, to the events of 1914. Whilst MacMillan continually stresses that there were always decisions which could have mitigated the final conflict's eruption, she also does not go too far into the whole nitty-gritty analysis of statesmen and events that more academic works normally do. The narrative is engaging, multinational, and covers the key "periods" in the leadup to 1914 (the Moroccan Crises, the turn of the 20th century, the Balkan Wars, etc.).
• Alternative #1: Dreadnought: Britain, Germany, and the Coming of the Great War by Robert Massie (1991) - This work is slightly outdated, and much more specific than MacMillan's, but it is arguably the pop-history book to read when it comes to understanding the Naval Arms Race between Britain and Germany (with lesser powers as well) that underscored tensions between 1906-1912. The work is much more of a biographically-minded one, following the rise (and fall) of the key figures in the arms race, including Churchill, Tirpitz, and Bismarck.
• Alternative #2: The Sleepwalkers: How Europe Went to War in 1914 by Christopher Clark (2012) - For a much more scholarly-minded work with some elements of pop-history narratives, look no further than this highly-reviewed and fairly well-known book by Clark. This is the type of book which lets you glimpse how historians in academia might actually analyse the origins of World War I, and it is rather thorough in investigating the origins of the conflict and the July Crisis of 1914. Mind you the work is not without its faults, notably a tendency to portray Russia, Serbia, and France as the responsible parties whilst avoiding the same accusations with Germany and Austria-Hungary. However, for a work which is understandable yet also engaging, it does the job well.

Prolongation

• Top pick: Pandora's Box: A History of the First World War by Jorn Leonhard (2018) - This most recent work has been very well-received, and historian Richard Evans called it "the best large-scale synthesis in any language of what we currently know and understand about this multidimensional, cataclysmic conflict." Leonhard's work is also supplemented with pictures and diagrams to help explain the First World War's course in Europe, the Middle East, and even the oft-omitted Asian theatre. He also delves into the Home Front and how the war impacted civilians as well as soldiers, with a note on the consequences of the conflict for the 20th century. A tad pricey to be certain, and a thick work as well (1060 pages or so), but well worth the read.
• Alternative #1: 1914-1918: The History of the First World War by David Stevenson (2012) - This work is much less of a deep-dive into all the aspects of the war as Leonhard's publication, but it does an excellent job of exploring all the major (and minor) military operations of the European fronts, as well as the larger sociopolitical changes which occurred during (and after) the conflict. Stevenson is a well-respected expert on the geopolitics of World War I, and this work is proof of that.
• Alternative #2: Castles of Steel: Britain, Germany, and the Winning of the Great War at Sea by Robert Massie (2007) - Consider this the sequel work to Dreadnought, as it deals with the naval theatre of the war and how Britain and Germany clashed on the water (as opposed to the land). Massie's work is well-researched, and this title is actually on here because of a friendly recommendation from fellow First World War flair u/IlluminatiRex (who is also particularly well-versed in all things nautical from 1914-1918).

Termination

• Top Pick: Paris 1919: Six Months that Changed the World by Margaret MacMillan (2001) - Margaret MacMillan not only has a great book on how the war began, but also on how it ended. For quite some time, this was the work on the Paris Peace Conference and the Treaty of Versailles, and it rightly deserves a place in your reading list for the First World War. The use of sources is thorough, decisions are analysed in-depth and with the consequences considered, but the narrative remains engaging throughout.
• Alternative #1: The Vanquished: Why the First World War Failed to End by Robert Gerwarth (2017) - This work is much more recent than MacMillan's, and it re-evaluates the impact of the end of World War I up until 1923. Whilst not explicitly "revisionist" in its treatment of the immediate postwar period, The Vanquished invites its readers to rethink the notion that the First World War "ended" on the 11 November 1918.
• Alternative #2: The Great War for Peace by William Mulligan (2014) - This work is rather revisionist in its approach to the whole idea that "The War to End All Wars" didn't really end anything. Mulligan challenges the mockery of World War I as a "pointless war" by arguing that as a result of the carnage and brutality of the conflict, the foundations for modern peacemaking processes and international politics. Engaging, scholarly, but also provocative, this work would be a good companion to Gerwarth's one above.

Hope these recommendations help, and feel free to ask any follow-up questions as you see fit.

My perspective comes from the central powers, since I focus a lot on German history, so:

Ring of Steel, by Alex Watson. This is a fairly in-depth study of the German and Austro-Hungarian home front, and how the people as a whole conceived of the war

Germans into Nazis, by Erich Kurlander. While not about the war itself, it’s about the legacy of the war, which is crucial for attempting to understand just how and why the war was so important to the German people

Germany’s Aims in the First World War, by Fritsch Fischer. This is older, but it is crucial for understanding the arguments about Germany’s role in the First World War, what Germany exactly wanted, and perhaps most crucially, it fits into the Sonderweg idea: a conception of German history whereby the Nazis were the final culmination of all the oddities in german culture when compared with Britain and France and America

I highly recommend 'A World Undone' by G.J. Meyer for a one volume summary. Entertaining and goes into the lesser fronts as well as the big ones. Good audiobook as well.

'The White War: Life and Death on the Italian Front 1915-1919' by Mark Thompson is great as well! Only covers one part obviously.

Those are my two favorites. 'The First World War: Germany and Austria-Hungary 1914-1918' by Holger H. Herwig is good but pretty thick.
People have strong opinions about Barbara Tuchman's books it seems but those strong opinions are written up online which makes the book arguably more useful from an educational perspective as you get fairly informed opinions 'on both sides'.

For those not in the know, r/askhistorians has a recommended reading list for questions just like this one!

https://www.reddit.com/r/AskHistorians/wiki/books/