Something like that. Simple theft seems to carry the idea that it was done as a spur-of-the-moment idea, or you took something to better your own situation. Larceny seems to give the connotation (according to the Wikipedia page) that you had to:
A) want to steal it
B) which implies foreknowledge and a plan
C) the person who you took it from knows that you took it, and when confronted, you would say that it was yours

So, yes, if I stole a car from my friend, and I told him that the car is mine after he filed a report, that would be larceny.

Of course, in this situation, the insurance on the car, as well as any form of vehicle registration would prove you wrong. Did that help?

EDIT: If you did something like a book, which has no inherent value until published, you're venturing into the realm of intellectual property, which has its own set of rules. Larceny deals with physical things that have value. A car that is purchased for $20k has value. A bunch of words you scribbled into a book does not.