Hi,
What languages are you able to read math in?
Generally these subjects are introduced at the same time as Taylor approximations. I know that English-language books tend to be weak on this point in comparison with foreign ones. (My best guess as to the reason is that the subject is a bit too complicated to be done well in basic calculus books but considered too elementary for analysis books.) There is a moderate amount of discussion of o-notation in Chapter 7 of "Calculus" by Apostol, for example (which has a Spanish translation).
The subject is usually covered excellently in French-language books for the first year of university in France or Switzerland, under the name "développements limités", at least in older ones.
The subject is a bit difficult to understand if you haven't done much work with the formal definition of the limit of a function or sequence.
Edit. For a CS-oriented presentation, also see Chapter 9 of "Concrete Mathematics" by Graham, Knuth and Patashnik, though I think it's best to have worked with the symbols, o, O, \~ in connection with Taylor series first.
