I would go with any of the "D&H in Color" books by Morning Sun Books,
they have 5 D&H books:
D&H Color Guide to Freight and Psgr. Equipment
Delaware and Hudson In Color, Vol. 1
Delaware and Hudson In Color, Vol. 2
Delaware and Hudson In Color, Vol. 3
Delaware and Hudson Steam In Color
Morning Sun books are generally very nice..(although IMO they are starting to get a bit too expensive, for the size of the books) but $45 is a decent value for most of them..they are nice hard cover books, usually about 120-130 pages..no one else does "all color" books like they do.
For a detailed history of the D&H (but no color photos) the best book is:
http://www.amazon.com/Delaware-Hudson-I ... 0815604556
this book goes way back to the origin of the D&H, has lots of nice B&W photos, but no color.
its more of a "in-depth history" book, as opposed to a "picture book"..
the Morning Sun books are heavier on the "picture book" side, and less heavy on the detailed history..
(although they do give some history too..and the photos have captions)
For a "first book" on the D&H, personally I would choose:
Delaware and Hudson In Color Volume 2
Jeremy and Jeffrey Plant
As the winds of change swept over Eastern railroads in the 1960s, the D&H entered its most exciting period. Exotic diesels such as PAs and Sharks, wild lashups of units bearing the colors of the D&H and former owners, and expansion into the large cities of the East characterize the D&H before the Guilford takeover in 1984. Join us in this 128-page hardcover for a trip over the D&H in the heady years between lightning stripes and Guilford.
Item # 1030
from: http://www.morningsunbooks.com/anthraci ... son%20Vol1
that looks like a nice "general" book on the D&H in the diesel era..
I dont have the book personally, but I would like to!
(I have a ton of other Morning sun books, on the LV, EL, and other railroads..im very happy with all of them)