Hello Cair and All,
My bees were very busy pollen yesterday in Northern Virginia. I thought it was too early for pollen.
The bulk of early pollen comes from trees such as Maples, Willows and Elms in the U.S.

Are there any books that list this info?
Most bee books have got some information.
Specific information can be found in

American Honey Plants  by Frank Pellet published by Dadant (1976)
Or  
Honey Plants of North America  by John H. Lovell  (Originally published 1926 but reprinted 1999)
A.I. Root offered a limited reprint of the book in 1999.  Some libraries still have the book. The reprint was a collectors item and only 250 copies were made. Maybe Kim Flottum will comment on the availability. 

Sincerely,
Bob Harrison
Odessa, Missouri