Titanic book? (5)

I believe the answer is:

atlas

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'book?' is the definition.
(I know that atlas is a type of book of facts)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(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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