Aspect choice is a little like articles in English
Take instruction manual, place back on bookshelf, go forth and communicate, for it is imperfective and so will you be. (I think that's the gist of it). Why do instruction manuals omit articles? Who knows?
The best I could find: 301 Polish Verbs by Klara Janecki.
Very reasonably priced too.
I have been meaning to indulge in the aforementioned text book, but never seem to get round to buying it, easy as doing so may be and at such a low cost as Mr. Sausage says. I have seen a few short lists of verbal twins, but I only ever really learn to speak the words I actually use. I can understand some of these twin words, but without actually remembering exactly what they are. Sometimes just understanding and being understood seem more important.