These May movies are based on books:
Jurassic Park 3D (the 3D release of the 1993 box office smash hit)
is still based on the novel Jurassic Park by Michael Crichton (iconic cover by the amazing Chip Kidd).
Hannah Arendt is a biographical film about the German Jewish philosopher. It isn’t based on any specific book,
but there are quite a few books about her, the times she lived in and her work, like The Portable Hannah Arendt.
Two Mothers is based on the short story The Grandmothers by Nobel Prize winner Doris Lessing.
The Great Gatsby is based on the classic written by F. Scott Fitzgerald. If you haven’t read it yet, do! Glorious use of language. 
The Company You Keep is based on the novel with the same title by Neil Gordon.
L’Ecume des Jours is based on the French novel with the same title by Boris Vian.
It has been translated to English with the title Froth on the Daydream.
Epic is based on the novel The Leaf Men and the Brave Good Bugs by William Joyce
(the same man who also wrote The Rise of the Guardians books).
Midnight’s Children is based on the modern classic by Salman Rushdie (originally scheduled for March).
