"The book was better than the movie," is what you hear the most, but there have been a few exceptions. I thought Gone With The Wind was an epic movie from an unremarkable book.
It didn't attain quite the cult status of Where Eagles Dare, but it's a great movie nonetheless. Force Ten From Navarone, not so much. As for Alistair MacLean's stories, one reviewer remarked that if the Allies had a cadre of MacLean characters available in 1939, WW II would have ended in six weeks, not six years.
I remember reading the book over 50 years ago and really enjoyed it. Some of the British terminology threw me off. Couldn't figure out why they were carrying torches.