Reddit mentions of European Union Politics

If you want a good grounding in European Union politics, since that is my speciality, I can help you there.

Firstly, I would avoid all of the 'airport' read books written by journalists of a particular bent pushing their narrative on today's politics or Brexit, so "All out War", etc. (This goes for whether you want more info about Westminster politics, or UK interaction with EU politics.) Whilst they may be entertaining, they're written to "push" a narrative or viewpoint of the author, and aren't meant to be neutral accounts or fact laden at all.

For EU affairs I recommend two textbooks that would be required reading for any undergraduate studying EU politics, and serve as a core quick reference texts for any postgrad looking at it too. These will help you to actually base your opinions on the EU on some core facts and/or well established arguments (something that is sorely lacking on here).

• European Union Politics (Fifth Edition) by Michelle Cini and Nieves Pérez-Solórzano Borragán
  
  
• The Government and Politics of the European Union (8th edition), The European Union Series by Neill Nugent
  
  Both of these should be fairly cheap to pick up second hand, but I do not recommend purchasing earlier versions than those I have listed, since a lot has happened in the intervening years since their previous editions were published.
  
  Both of these textbooks are laid out in a concise and simple to follow manner, with key infoboxes for further reading and detail. They both look at theories of integration (why member states chose to integrate/who are the actors), the history and evolution of the Union, and the logic behind certain policies, how its institutions operate and have evolved, how they interact with each other both in theory and practice, arguments as to what the "Union" is, and finally critiques (and counterarguments to them) of the Union and its policies.
  
  You can either read through them chapter by chapter, or keep them at hand, and when something comes up, flick through and examine them.
  
  I can recommend further text books if you so wish.
  
  Edit: PS. I see others on this post are recommending several political theory texts from 17th century authors and later. My tip is to find textbooks on political theory if that is something you want to look into. Whilst those texts are important, there are many interpretations of them and their often flowery, and to put it bluntly longwinded prose, (Hobbes taking several pages to discuss what is "power" springs to mind) can make digesting them difficult. A good textbook will digest the key arguments from political theory texts and lay them out in a nice concise manner, with critiques and counter arguments. You can then go and read the actual texts that stand out if you so wish.

https://www.amazon.co.uk/dp/0198749953/?coliid=I1VZM8NH4D8427&colid=2ZKBN4RSJSYJV&psc=0&ref_=lv_ov_lig_dp_it - Catherine Barnard - The Substantive Law of the EU: The Four Freedoms.

https://www.amazon.co.uk/dp/0198789130/?coliid=I3FQZDCZWZQQW7&colid=2ZKBN4RSJSYJV&psc=0&ref_=lv_ov_lig_dp_it - Catherine Barnard and Steve Peers (as mentioned above, he is really very good)

https://www.amazon.co.uk/dp/0198708939/?coliid=I2G9WKHW05Z4U3&colid=2ZKBN4RSJSYJV&psc=0&ref_=lv_ov_lig_dp_it - EU Politics.

https://www.amazon.co.uk/Institutions-European-Union-New/dp/0198737416/ref=sr_1_fkmr1_2?s=books&ie=UTF8&qid=1524610636&sr=1-2-fkmr1&keywords=dermot+oleary+eu - Dermot Hodson, John Peterson 9eds) - Institutions of the EU.

A simple look on Amazon or Oxford University Press/Routledge etc will give you a great start for this type of text book and references will point you to further reading if you find yourself interested. The links I posted are most recent versions which I have read a bit but this type was my UG and PG essentially.