The ISBN of Nightchild is 0-575-07300-4.
the anser to puzzle 073 is simply can A
073
It has no value since 4 does not appear in 073!
No
It is #073
.073
1 073 741 824 bytes ==
1 073 741 824
The ISBN of Biswasghatak is 81-7612-073-1.
073-2557-6815-533
New York State