Reddit reviews John Constantine, Hellblazer: Reasons to Be Cheerful

I'd read The Saga of the Swamp, mostly just because it is amazing, first, and it is his original introduction. But if you just wanna jump right into John's stories I would say the best techniques is to jump on to the run of the writer you like best. If you are familiar with comics, especially vertigo comics, at all you will be familiar with many of the creators including Jamie Delano, Warren Ellis, Garth Ennis, Mike Carey, Brian Azzerello, and Pete Milligan among many others. There are also short runs from other famous writers such as; Grant Morrison, Neil Gaiman, Jason Aaron, and more, that are worth checking out.

If everything else I said is meaningless to you. I would most readily recommend Mike Carey and Garth Ennis' runs.
Here are the Ennis Trades (6 or 7 are my favorite, but they must be read in order:
http://www.amazon.com/John-Constantine-Hellblazer-Dangerous-Edition/dp/1401238025/ref=sr_1_6?ie=UTF8&qid=1414271898&sr=8-6&keywords=hellblazer

http://www.amazon.com/John-Constantine-Hellblazer-Vol-Bloodlines/dp/1401240437/ref=sr_1_8?ie=UTF8&qid=1414271898&sr=8-8&keywords=hellblazer

http://www.amazon.com/John-Constantine-Hellblazer-Vol-Tainted/dp/1401243037/ref=sr_1_7?ie=UTF8&qid=1414271898&sr=8-7&keywords=hellblazer

http://www.amazon.com/John-Constantine-Hellblazer-Vol-Graphic/dp/1401247490/ref=sr_1_9?ie=UTF8&qid=1414271898&sr=8-9&keywords=hellblazer

Here are the Carey Ones (they can be read in any order All His Engines is particularly a stand alone graphic novel - My favorite is The Red Sepulchre):

http://www.amazon.com/John-Constantine-Hellblazer-Red-Sepulchre/dp/1401204856/ref=sr_1_4?ie=UTF8&qid=1414272092&sr=8-4&keywords=hellblazer+carey

http://www.amazon.com/John-Constantine-Hellblazer-Stations-Cross/dp/1401210023/ref=sr_1_3?ie=UTF8&qid=1414272092&sr=8-3&keywords=hellblazer+carey

http://www.amazon.com/John-Constantine-Hellblazer-Reasons-Cheerful/dp/1401212514/ref=sr_1_1?ie=UTF8&qid=1414272092&sr=8-1&keywords=hellblazer+carey

http://www.amazon.com/John-Constantine-Hellblazer-All-Engines/dp/1401203175/ref=sr_1_6?ie=UTF8&qid=1414272092&sr=8-6&keywords=hellblazer+carey