Titanic book? (5)

I believe the answer is:

atlas

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'book?' is the definition.
(atlas is a kind of book)

I cannot understand how the remainder of the clue works.

(Other definitions for atlas that I've seen before include "It appears at the top of the spine" , "Set of charts" , "Asian satin" , "I carry a huge weight" , "A geog. book; N. African range" .)

I've seen this clue in the Evening Standard.

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