Hi there.
I've found these books very useful:
Polish in 4 weeks - a lot of info packed into a really small space, gives you a bit of headache, but there are some hilarious dialogues - the two girls talking about Waldek had me in fits. :) It's the best book for vocab I've read yet as well, there's a quite hefty list of vocab in every section that I try to write out and then pin to the fridge or something - takes about a week to properly learn the vocab and gives you info on grammar as well.
301 Polish Verbs by Klara Janecki - very very helpful, a must buy
Hurra po polsku is a much more informative, gentle paced book. My teaching in Poland basically taught me from it - has some quite helpful tables for learning cases better as well. Best bet would be find someone who's going to Poland to get it for you, or to get it from a web shop. It costs about 95zl in Poland for the podręcznik studenta and ćwicień, but they were trying to charge me £40 for it in the UK (over 160zl)! You can get it from
www.eksiegarnia.pl in Krakow, and they delivered it to the UK for me.
Lessons are definately the best way though, gives you more motivation to learn - fear of the nauczyczelka! Teacher's are usually able to explain grammar to you much better than books - but the books are a good reference.
Haven't read any of the others yet, so can't comment.
Good luck
Chris