I've been doing a decent bit of shark and tuna fishing out in Mass Bay and nearby reagions over the last few years--it's very addictive and the learning curve is huge. Going out with people is by far the best means of learning, but there are some decent tuna and shark fishing books. Off the top of my head, two are:
Fishing for Sharks--Pete Barret (i think)
To Catch a Tuna--Al Anderson
THere are a few more good ones--drop me a line and I'll dig up the rest of the titles and tell you the little I know about the area.