"Easy" is a hard word. I'm just coming back to the keyboard after 30+ years away and I can't say what level of player I was when I left (past Fur Elise; stalled on the Moonlight Sonata). Have been buying a host of popular music for "easy" piano and it varies. Some is so simplified I have it down on the third time through; others send me to the flash cards to learn what those off-staff notes are. LOTR is right in the middle of the range.
--A few songs from each of the three movies. In Dreams and Concerning Hobbits are the ones I'm learning first; will go back to the DVD and listen differently to decide which of the remaining songs I liked enough to want to learn.
--For the most part, no more than four notes in play at any one time, and a lot places where the music is one note, each hand. A smattering of 16th notes but mostly quarters, some eighths, and half notes.
--Easy key signatures; mostly C and the rest two sharps or two flats max.
--Lots and lots of 12-note arpeggios without a lot of fingering assistance in the left hand.
--Notes range two octaves above and below middle C.
In sum? There are enough notes on each page that the song sounds good, yet easy enough to recognize the tune on the first or second time through. Plan: master this book, then buy the individual movie scores one at a time as I get better and want a richer sound.