The Lion, The Witch and The Wardobe

In the book, the battle takes up only a page or two. Definitely different source material than LOTR. Lewis & Tolkein were friends and colleagues though, and read each other's work.

No trilogy this; if it does well they should get all seven books made into films, I would guess. The Lion, The Witch, and The Wardrobe was the first of the books written and ought to stand up as an introduction to Narnia, but there was a later book that takes place first and explains how Narnia came to be. Most omnibus volumes put The Magician's Nephew first as that's how C.S. Lewis preferred they be read once he finished the series, but TLTW&TW was published first and was the first book of the series read by many people, including myself when I was 10ish -- Foe