Written by Brian Michael Bendis as one of the anchors for Marvel's "Marvel NOW!" initiative, the original X-Men from the 1960's come forward to the present, causing all manner of havoc. It is surprisingly easy to get into was a new reader, which is a testament to Bendis's strength as a writer.
Focusing on Cyclops's more militant X-Men group, including Magneto, Emma Frost, and Magik. We acknowledge that this one is had its ups and downs in certain ways (the stretch spent in Limbo is called out [even though I was fine with it -Meddling Moisés]), but it continues to be a very good (indispensable, really) companion to All-New X-Men. This is especially the case after the Battle of the Atom crossover concluded in late 2013.
Giant Size X-Men #1
We didn't actually talk about this one very much (expect that in the next X-Men episode), but it is referenced throughout. This 1980s reboot of the team was a big launching point, and remains one of the most accessible ways to get into the world.
Dubbed "the Nightcrawler book", this one is only three issues in at the time of this posting, but is loads of swashbuckling fun, and is written by one of our favorite writers, Jason Aaron (Thor: God of Thunder). The book follows an interesting combination of X-Men going to rescue Nightcrawler from the afterlife.
This yearly subscription service is growing by leaps and bounds every few months. For example, the aforementioned Amazing X-Men had its first issue made free on the service when the series launched.
Days of Future Past
As iconic as this series is, people often forget that it takes place over the span of two comic book issues. There's an X-Men movie with this as a subtitle coming out this year, and we figure that it might be on many to-read lists this year. It is not an ideal entry point, because it needs some context before it can work very well for you. This is a great example of how concentrated major storylines could be 20+ years ago.
God Loves, Man Kills
The fifth "Marvel Graphic Novel" is steeped in the 1980s: religious extremism, jingoism, and other unmistakable themes of the era. Like Days of Future Past before it, this one is a much better contextual read. It may not work as a perfect jumping in point, but it's pretty close. This thing bleeds civil rights allegory that is all over the X-Men canon, ever since their creation. The art, from pencils to inks to color to lettering, is absolutely beautiful. This is one of those X-Men stories that delivers on all fronts in every way that it can. You just have to be into this sort of story. Interestingly enough, it is directly referenced in Bendis' current X-Men runs on All-New and Uncanny.
The Dark Phoenix Saga
This is the biggie, the top dog, the one that has been adapted as often as the X-Men have crossed into other media (movies, animated TV shows, and so on). Jean Grey acquires some major powers all of a sudden, things go very far south, and the effects are far-reaching throughout X-Men history. Her character arc student out as a more complex female comic book character than (many would argue) had been seen before. Without spoiling the who, the what, and the when of it (the cover seems to spoil something), some major death occurs that goes on to define many aspects of the next three decades of the X-Men in various respects.