restrictive/non-restrictive

[Navi]

Are these sentences correct:

1-I read his book about the Big Bang.
2-I read his book which is about the Big Bang.


3-I read his book, about the Big Bang.
4-I read his book, which is about the Big Bang.

Do "1" and "2" necessarily imply that he has written more than one book?
Do "3" and "4" necessarily imply that he has written only one book?

[Beeesneees]

2 and 4 imply he has written one book, but it is only an implication and not definite.
1 and 2 do not imply anything about the number of books written.

I would not use commas with those sentences (particularly 3) as there is no additional phrase following on from the secondary clause.
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