It was, in fact, the book in which he looked when he wished to admire himself.
"It is odd," said Cleggett, "that so clever a man should write down his own story in this way." "This book," said Farnsworth, "would be a boon to a psychologist interested in criminology.

You say it is odd.

But with a certain type of criminal, it is almost usual.

The human soul is full of strange impulses.

One of the strangest is towards just this sort of record.
Cunning, and the vanity which destroys cunning, often exist side by side.