I do understand the criticism of Gregory Peck. His character seems too young and not nearly tortured enough to do Ahab full justice.

The book obsesses about the religious significance of everything. You get a flavour of that with this film too, with superstition seamlessly blended in as well. Orson Wells awesome cameo as the preacher sets up and supports this important plot element. Important because, this is how men thought and dealt with the ongoing risk associated with seafaring. They were literally at the mercy of nature & the elements for months & years at a time.

An enduring image of the film for me is the scene where a member of the crew is seen carving patterns on Queequeg's (already heavily decorated) body using a knife. Queequeg himself is stoic and resigned to die at this point. Ishmael though, is outraged on discovering this abuse of his friend. This is unique to the screenplay, and is a brilliant dramatic instrument.

Ahab: 'From hell's heart I stab at thee; for hate's sake I spit my last breath at thee.' This line was also borrowed by Ricardo Monteban's Khan in 'The Wrath of Khan'.

Melville was inspired to write his tale by the personal account of Owen Chase, the son of a survivor of the Ship Essex, sunk by a whale in the Pacific. The whale charged twice; knocking itself out the first time.

Houston's film seems to capture a flavour of the period. It's probably substantially inaccurate, but it's nevertheless convincing. No other version of Moby Dick I've seen has been able to pull that off.