"Need" may be a strong word. Odds are that, considering Marvel have already presold over half a million copies of Secret Wars #1, that they will do their best to make it as self contained as they can.
I'm told that the final issue of Ultimate Spider-Man will have a "red skies" ending rather than contributing towards the plot. The final issue of the Fantastic Four may be heading that way too, collected in Fantastic Four Volume 4: The End is Fourever.
But when it comes down to it, reading Secret Wars #1-#8 should be enough. You won't have to read anything before. And Marvel's checklist of books you could read serves only to give background to some of the spinoffs.
But if you did want to read something before, here are some ideas.
Jonathan Hickman's run on The Avengers and New Avengers has been setting up Secret Wars. And it should all be nicely available. It also happens to be really good, Bleeding Cool named it one of the top eleven comics of the year.
Avengers Volume 1: Avengers World (Avengers #1-6)
Avengers Volume 2: The Last White Event (Avengers #7-11)
Avengers Volume 3: Prelude to Infinity (Avengers #12-17)
New Avengers Volume 1: Everything Dies (New Avengers #1-6)
Infinity ( Infinity #1-6, New Avengers #7-12, Avengers #14-23, Infinity: Against the Tide Infinite Comic 1-2)
Avengers Volume 5: Adapt or Die (Avengers #24-28)
New Avengers Volume 3: Other Worlds (New Avengers 13.INH, 14-17)
Avengers Volume 6: Infinite Avengers (Avengers #29-34)
New Avengers Volume 4: A Perfect World (New Avengers #18-23)
Avengers: Time Runs Out Volume 1 (Avengers #35-37, New Avengers #24-25)
Avengers: Time Runs Out Volume 2 (Avengers #38-39, New Avengers #26-28)
And the remaining few issues after those you can pick up in store….Then, if you want to go further back, you might choose
Fantastic Four by Jonathan Hickman Omnibus Volume 1 and Volume 2 or even Secret Warriors Omnibus and S.H.I.E.L.D.: Architects of Forever because you just never know.
Then there's Hickman's recreation of the Ultimate Mister Fantastic in Ultimate Comics Ultimates by Jonathan Hickman – Volume 1 and Volume 2. And there's the previous Secret Wars volumes Secret Wars, Secret Wars II – actually you may need Secret Wars II Omnibus if only for the Fantastic Four issues that Hickman has been heavily referring to. But you could just scrub all of this and go with Secret Wars Prelude instead.
That should do you. Though I wonder how Hickman will incorporate a certain Beyonder/Secret Wars based issue of New Avengers: Illuminati?
Have fun in there…
Any other recommendations?