The Dark Phoenix Saga is a classic.

If you want to spend a bit more than that, there is also a Legion omnibus which is awesome and would be right up his alley as a Legion TV fan.

u/SanchoPandaVTW · 6 points r/LegionFX

I like using comixology (comic ebook app via amazon), mainly because most graphic novels are a lot cheaper on it.

The one I'm reading isn't exclusively Legion focused, but covers past treatments.

The best Legion story is probably the 2012-2014 25 issue run: X-Men Legacy: Legion Omnibus.

u/TantumErgo · 6 points r/LegionFX

It’s very inspired by the specific (and great) comic X-men Legacy. It was hard to see how it was inspired by this in season 1, but as the series has progressed it has become clearer.

However, it is its own thing: the show isn’t trying to fit into any existing canon, movies or otherwise.

u/Tigertemprr · 3 points r/comicbooks

Spurrier

u/atomsk404 · 2 points r/LegionFX

Is this everything? X-Men Legacy: Legion Omnibus https://www.amazon.com/dp/1302903926/ref=cm_sw_r_cp_apa_i_yo6pDb823KRY4

u/CorruptedEvil · 1 point r/comicbooks

https://www.amazon.com/X-Men-Legacy-Omnibus-Simon-Spurrier/dp/1302903926

u/Neipalm · 1 point r/comicbooks

Is this the X-men legacy omni you mentioned? https://www.amazon.com/X-Men-Legacy-Omnibus-Simon-Spurrier/dp/1302903926

u/Crimsonking895 · 1 point r/LegionFX

I dont know when it was written but i bought it at a Chapters store right after season 1 aired.

https://www.amazon.ca/X-Men-Legacy-Omnibus-Simon-Spurrier/dp/1302903926/ref=asc_df_1302903926/?tag=googlemobshop-20&amp;linkCode=df0&amp;hvadid=292942072208&amp;hvpos=1o1&amp;hvnetw=g&amp;hvrand=8101907076132790198&amp;hvpone=&amp;hvptwo=&amp;hvqmt=&amp;hvdev=m&amp;hvdvcmdl=&amp;hvlocint=&amp;hvlocphy=9000834&amp;hvtargid=pla-302881205273&amp;psc=1