The best and most reasonably priced collection I have ever come across is 'Jolly Sailor Bold (Camsco 2010)-
232 sea songs and shanties, all with tunes, extremely well annotated with comprehendable but scholarly notes and pretty comprehensive bibliography
Highly recommended as far as I'm concerned
   
I think I got mine direct from the publisher but you might try The Book Depository and save the cost of the postage
Jim Carroll