If so, then the Offshore Sea Life ID Guide may be for you! Fair warning, Princeton Press sent me a free review copy. This one deals just with the East Coast.
I was ill-prepared from a sea-sickness standpoint for the pelagic we did this last summer. I would expect that by the time next spring rolls around I'll have forgotten the depths of misery that I (couldn't quite) stomach and will be willing to re-try it. Written by Steven Howell and Brian Sullivan, it's more of a handbook, checking in at a mere 64 pages. The first 10 or so are intros, the next 10-15 pages deal with whales. Pelagic birds account for pages 26-50. Here's a sample plate.
There's another 5 pages on flying fish which I would certainly have appreciated on our pelagic; we saw a good number of flying fish and I would have liked to have known more about them.
Finally the book deals with some of the billfish, rays, and sharks that are possibilities to encounter.
The book is a fun mix of fairly targeted plates dealing with some difficult to identify birds along with more general info about some of the other sealife that could be encountered on a pelagic. While I was surprised when I received it how short the book is, the small size will definitely increase it's usability in the field. At $14.95, I think this is a worthwhile investment for a birder planning to return to the Atlantic seas.