For the fun of it, during the last 3 years I have collected most every Delphi and Pascal book I came across. There are more than you think! :-) And they don't cost too much used at Amazon either. So I can say that if it's OOP you want, then Cantu's Object Pascal Handbook is top of the line and for the most part very useful for FreePascal and Lazarus. There are other books that cover OOP pretty good too but not by far as thorough as Cantu. Carlie Calvert's "Delphi Unleashed" contains a number of chapters and is a big allround, useful and easy to read "bible". I am pleased with first edition from 1995. Then there is Cantu's "Mastering Delphi 4, 5, 6 or 7". and Delphi Developers guide. Consider buying them all, you will learn new stuff from each of them.