Nowadays there are many books that may serve
as a starting point for reading about OO.
Dependent on your interest, you may look
at [Surviving], which treats issues of OO project management,
[Meyer97], which gives an extensive introduction to
design by contract and programming in Eiffel, or
[Fowler97], which gives a succinct introduction to
Alternatively, you may take one of the introductory
programming books for Java, from which you will almost certainly
learn something about OO as well.