As 3.0 or as 2.0

i’ve been messing around with flash for a year or two now but never really started getting into action scripting until about six months ago, with mx 2004… i took a break for a month or two, during which i aquired cs3, and just not starting playing with it. i know a semi-decent amount of 2.0, but have no clue what is different with 3.0… i have no idea what classes, extentions, handlers, etc are… my question is… since i obviously have a lot to learn, should i just continue learning 2.0 first, or just go ahead and start with the 3.0, and in either case, could anybody recommend some really good books??

thanks guys,
omni